A.T. – Appalachian Trail, a long-distance hiking trail in the eastern United States.
Altitude sickness – A group of symptoms that occur at high elevations due to reduced air pressure and lower oxygen levels. Symptoms can include headache, nausea, and shortness of breath.
Backcountry – Remote, undeveloped areas that are typically accessed by hiking or other means of human-powered travel.
Base weight – The weight of a backpacker’s gear, excluding consumables such as food, water, and fuel.
Blaze – A colored mark, usually painted or attached to a tree, to indicate the path of a hiking trail.
Bivouac (Bivy) – A temporary shelter or campsite, often used by climbers or minimalist backpackers.
Cairn – A man-made stack of stones used to mark a trail or a summit.
Cat hole – A small hole dug in the ground for the purpose of burying human waste while hiking or camping.
CDT – Continental Divide Trail, a long-distance hiking trail that follows the Continental Divide in the United States.
Class – A system used to rate the difficulty of hiking and climbing routes, with Class 1 being the easiest and Class 5 requiring technical climbing skills.
Crampons – Metal spikes that attach to the bottom of boots to provide traction on snow and ice.
Cross-country – Traveling off-trail or away from established paths.
Double blaze – Two trail blazes placed close together, typically indicating a turn or change in direction.
Down – Insulating material made from the soft under feathers of ducks or geese, used in sleeping bags and clothing.
Elevation gain – The total vertical distance ascended during a hike or climb.
ETA – Estimated Time of Arrival, the approximate time at which a hiker expects to reach their destination.
FKT – Fastest Known Time, a record time for completing a specific trail or route.
Ford – A shallow point in a river or stream where it can be crossed on foot.
Gaiters – Protective coverings worn over boots and lower pant legs to keep out debris, snow, or water.
GORP – Good Old Raisins and Peanuts, a popular trail snack also known as trail mix.
GPS – Global Positioning System, a satellite-based navigation system that can be used to determine one’s location while hiking.
Hiker midnight – The time at which hikers tend to go to bed, typically shortly after sunset.
HYOH – Hike Your Own Hike, a phrase that encourages hikers to choose their own pace and style of hiking.
ISO – International Organization for Standardization, a group that sets standards for various products, including some outdoor gear.
LNT – Leave No Trace, a set of principles promoting responsible outdoor ethics and minimizing human impact on the environment.
LWD – Long Water Carry, a section of trail where water sources are scarce and hikers must carry extra water.
MSR – Maximum Sustainable Rate, the fastest pace at which a hiker can travel without becoming overly fatigued.
NOBO – Northbound, referring to hikers traveling north on a long-distance trail.
NPS – National Park Service, the U.S. federal agency responsible for managing national parks and monuments.
Out-and-back – A type of hike that follows the same route to a destination and then returns to the starting point.
PCT – Pacific Crest Trail,
a long-distance hiking trail that runs from the United States-Mexico border to the United States-Canada border, passing through California, Oregon, and Washington. 32. Peak bagging – The pursuit of reaching the summits of multiple mountains, often with the goal of completing a specific list or challenge.
Permits – Official documents or passes required for access to certain trails, campsites, or wilderness areas.
PUDs – Pointless Ups and Downs, a term used to describe a series of small, seemingly unnecessary climbs and descents on a trail.
REI – Recreational Equipment Inc., a popular retailer of outdoor gear and clothing.
Ridge line – A long, narrow stretch of elevated land connecting two or more mountain peaks.
Rime ice – A type of ice that forms when supercooled water droplets freeze upon contact with solid surfaces, such as trees or rocks.
Scrambling – A type of climbing that falls between hiking and technical rock climbing, often involving the use of hands for balance and support.
SOBO – Southbound, referring to hikers traveling south on a long-distance trail.
Summit – The highest point or top of a mountain or hill.
Switchback – A zigzagging section of trail designed to reduce the steepness of an ascent or descent.
Thru-hiking – The act of hiking a long-distance trail from end to end in a single, continuous journey.
Topo map – Topographic map, a type of map that shows the physical features of a landscape, including elevation contours, streams, and other landmarks.
Trailhead – The starting point or entrance to a hiking trail.
Trail magic – Unexpected acts of kindness or support provided to hikers by trail angels, such as food, water, or transportation.
UL – Ultralight, a style of backpacking that emphasizes carrying the lightest and most minimalist gear possible.
Water source – A natural or man-made source of water, such as a stream, spring, or faucet, where hikers can refill their bottles or containers.
White blaze – The white-painted mark used to designate the path of the Appalachian Trail.
Wilderness area – A designated region of public land that is protected and managed to preserve its natural condition and minimize human impact.
YDS – Yosemite Decimal System, a rating system used to classify the difficulty of hiking and climbing routes.
Zero day – A day when a long-distance hiker takes a break from hiking to rest, resupply, or tend to other needs.