Trail Running Glossary A–Z

Trail running has its own language. From technical terrain and elevation terms to race formats, kit, and trail culture, understanding the terminology can make the sport far more accessible — whether you’re brand new to the trails or deep into ultras and mountain races. This trail running glossary has been created to explain the most commonly used trail running terms in clear, practical language.

Terrain & Trail Terms (A–Z)

All‑Mountain

A style of trail running that covers varied terrain such as forest trails, ridgelines, rocky paths, scree, and alpine ground. Common in mountain and European-style races.

Bog

Soft, waterlogged ground often found on moorland and fell terrain. Boggy sections slow pace dramatically and demand strength and balance.

Bridleway

A public right of way shared with horses and cyclists, particularly common in the UK. Usually wider and less technical than footpaths.

Bushwhacking

Running off marked trails through vegetation, heather, forest, or wild terrain. Often seen in adventure racing or self-navigated routes.

Crest

The highest point of a climb, ridge, or mountain before descending.

Descent

The downhill portion of a trail. Descents can be fast and runnable or steep and technical, requiring strong downhill skills.

Doubletrack

A wide trail or access road that can accommodate vehicles. Often referred to as fire roads or forestry tracks.

Fell

A UK-specific term referring to upland or mountainous terrain. Fell running traditionally involves steep climbs, rough ground, and minimal markings.

Fire Road/Track

A wide gravel or dirt track used for forestry or emergency access. Typically less technical but often steep and exposed.

Moorland

Open, exposed terrain commonly found in the UK. Moorland routes may include bog, grass, and little shelter from weather.

Ridgeline

A narrow trail running along the crest of hills or mountains, often exposed but offering wide views.

Rooty Trail

A trail section with exposed tree roots that requires careful foot placement.

Scree

Loose rocks found on steep slopes. Scree descents require confidence and controlled movement.

Singletrack

A narrow trail allowing only one runner at a time. One of the most searched trail running terms and prized for flow and immersion in nature.

Switchbacks

Zig-zagging turns used to manage steep climbs or descents by reducing gradient.

Technical Trail

Trail terrain that requires focus and agility due to rocks, roots, steep gradients, or uneven ground.

Elevation & Distance Terms (A–Z)

Ascent

The total amount of climbing during a run or race.

Backyard Ultra

A last-runner-standing race format where participants complete a 6.7km loop every hour until only one runner remains.

Cumulative Elevation Gain

The total vertical ascent across a route, regardless of descents in between.

Drop

The total amount of downhill descent during a run.

Elevation Gain

The total vertical climbing during a run. Often referred to as vert.

FKT (Fastest Known Time)

An unofficial speed record set on a specific trail or route.

Laps

Repeated loops of the same course within a race.

Negative Split

Running the second half of a race faster than the first.

Segment

A defined section of trail, often timed using GPS platforms.

Vert

Short for vertical gain. A commonly used trail running term when describing climbing.

Vertical Kilometre (VK)

A short race with 1,000 metres of ascent over minimal distance.

Training & Performance Terms (A–Z)

Aerobic Base

Foundational endurance fitness developed through easy and steady running.

Bonk

Sudden fatigue caused by glycogen depletion.

Cadence

The number of steps taken per minute.

Cut‑Off Time

The maximum time allowed to reach a checkpoint or finish a race.

Deload

A planned reduction in training volume to allow recovery.

Effort‑Based Pacing

Managing intensity based on perceived effort rather than pace.

Fartlek

Unstructured speed play during a run.

Hill Repeats

Repeated uphill efforts used to build strength and climbing efficiency.

Long Run

An extended endurance run forming the backbone of trail training.

Power Hiking

Fast walking on steep climbs where running is inefficient.

Taper

Reducing training volume before a race to allow full recovery.

Race & Event Terms (A–Z)

Aid Station

A checkpoint providing water, food, and sometimes medical support.

Bib

The numbered race identifier worn by runners.

Mandatory Kit

Safety equipment required by race organisers, often including waterproofs and navigation tools.

Point‑to‑Point

A race that starts and finishes at different locations.

Self‑Navigation

Races where runners must follow maps or GPX files without course markings.

UTMB Index

A ranking system used for qualification into UTMB World Series events.

Gear & Kit Terms (A–Z)

Bladder

A bladder is a soft, flexible water reservoir carried inside a running vest or pack. It allows hands-free hydration via a drinking tube and is commonly used on longer trail runs and ultra races where carrying larger volumes of fluid is essential. Bladders typically range from 1 to 2 litres and sit close to the back to minimise movement while running.

Drop Bag

A drop bag is a personal bag placed at designated checkpoints during long trail races and ultramarathons. Runners use drop bags to store spare clothing, shoes, nutrition, or mandatory kit, allowing them to resupply without carrying everything from the start. Drop bag locations and rules are set by race organisers and vary between events.

Gaiters

Gaiters are fabric covers worn over trail running shoes and around the ankles to prevent debris such as stones, mud, sand, or snow from entering the shoe. They are especially useful on rocky, sandy, or muddy terrain and in fell or mountain running. Some trail shoes have built-in attachment points for lightweight gaiters.

GPX File

A GPX file is a digital route file containing GPS data such as distance, elevation, and waypoints. GPX files are commonly used in trail running for navigation, particularly in self-navigated races or remote routes. They can be uploaded to GPS watches, mapping apps, or handheld devices to help runners follow a course accurately.

Poles

Poles, or trekking poles, are collapsible sticks used by trail and ultra runners to assist with balance and efficiency on steep climbs and descents. They help reduce strain on the legs, improve stability on technical terrain, and are commonly used in mountainous races. Poles are often carried folded in a quiver or attached to a running vest when not in use.

Trail Shoes

Trail shoes are running shoes specifically designed for off-road terrain. They feature enhanced grip through aggressive outsole lugs, increased stability, and added protection against rocks and roots. Trail shoes vary widely in cushioning, heel-to-toe drop, and firmness, with different models suited to muddy trails, rocky ground, or long-distance ultras. Available in waterproof, different types for different terrain and wider models for those who need wide fit trail running shoes, there is plenty to choose from.

Vest Pack

A vest pack is a lightweight backpack worn close to the body, designed to carry essential kit such as water, nutrition, extra layers, and safety equipment. Unlike traditional backpacks, vest packs distribute weight evenly across the torso to minimise bounce and improve comfort while running. They are a staple piece of gear for trail runners and ultra athletes.

Nutrition & Hydration Terms (A–Z)

Electrolytes

Minerals lost through sweat that must be replaced during long runs.

Fueling Strategy

A planned approach to energy intake during training or races.

Gel

A concentrated carbohydrate source used during endurance efforts.

Real Food

Whole-food options such as potatoes, rice balls, or sandwiches used during ultras.

Navigation & Tech Terms (A–Z)

Altimeter

An altimeter is a device or sensor used to measure elevation above sea level. In trail running, altimeters are commonly found in GPS watches and handheld devices and are used to calculate elevation gain, descent, and total vert. Barometric altimeters tend to be more accurate than GPS-only elevation data, particularly in mountainous terrain.

GPS Watch

A GPS watch is a wearable device that tracks distance, pace, time, elevation, and route using satellite positioning. Trail runners rely on GPS watches to monitor effort, follow GPX routes, record elevation gain, and analyse performance after runs. Many trail-specific GPS watches include features such as navigation, altimeters, weather alerts, and long battery life for ultra-distance events.

Heatmap

A heatmap is a visual representation of popular running routes created from aggregated GPS data. Heatmaps show where runners most commonly run and are often used for route planning, discovering new trails, or assessing how frequently a path is used. In trail running, heatmaps can help identify established routes, technical sections, or quieter trails away from busy areas.

Trail Culture & Community Terms (A–Z)

Crew

Crew are the people who support a runner during long-distance trail races and ultramarathons. They typically meet runners at designated checkpoints to provide food, drink, clothing changes, equipment, and encouragement. A good crew can make a significant difference to a runner’s performance, morale, and safety during ultra events.

DFL (Dead Last Finisher)

DFL stands for Dead Last Finisher and is often worn as a badge of honour in the trail running community. In trail running, finishing the race — regardless of position — is widely respected, especially in tough conditions or ultra-distance events. Being DFL often represents resilience, determination, and grit rather than failure.

Trail Magic

Trail magic refers to unexpected acts of kindness or support found on the trail, such as spectators offering food and drink, a friendly cheer from a stranger, or help from another runner. Trail magic embodies the supportive, community-driven spirit that makes trail running unique compared to many other endurance sports.

Ultra Runner

An ultra runner is someone who competes in ultra-distance races, defined as any event longer than the traditional marathon distance of 26.2 miles (42.2km). Ultra runners often tackle extreme distances, elevation gain, and technical terrain, relying as much on mental resilience and strategy as physical fitness.

And there are these…

Trail Running Slang & “You Had to Be There” Terms

Trail running isn’t just about miles and elevation — it also comes with its own humour, shared suffering, and unspoken understanding. These terms may not appear in official race guides, but if you run trails long enough, you’ll hear (or live) them.

Type 2 Fun

An activity that is absolutely not fun while you’re doing it but becomes fun in hindsight. Common symptoms include swearing on climbs, questioning life choices, and signing up for another race anyway.

Trail Legs

That magical (and rare) feeling when your legs suddenly stop complaining and everything feels smooth, strong, and runnable — usually for a very short window before reality returns.

Send It

A phrase meaning to fully commit, often used before a sketchy descent or questionable decision. Results may vary.

That Didn’t Go to Plan

A catch-all phrase covering wrong turns, unexpected weather, missed cut-offs, cramp, bonking, or all of the above.

It Looked Runnable on the Profile

What someone says before discovering the climb is steeper, longer, and far more soul-destroying than expected.

Only a Short Climb

A relative term in trail running that usually means “much longer than you think.”

Respect the Distance

A reminder often ignored by beginners and learned the hard way. Distance on trails rarely equals distance on the road — elevation, terrain, and weather all matter.

Never Again

A statement commonly made immediately after finishing a race and almost always followed by a new entry the next morning.

This glossary will continue to grow as trail running evolves. Bookmark this page as a reference, or explore other Running For The Hills guides to deepen your trail running knowledge.