Bivy (bih-vee): Short for the French word 'bivouac,' this term can refer to a night out without traditional shelter (i.e. tent or full sleeping bag) or an extremely lightweight mylar sack that is used in place of a sleeping bag.
Blazing: Refers to the act of thru-hiking by following the painted markers along the Appalachian Trail. May also be color-coded:
Whiteblazing: Main AT trails
Blueblazing: AT side trails
Aquablazing: Taking a waterway to bypass a section of trail.
Pinkblazing: When a male hiker speeds up or slows down in order to stay with a female hiker.
Yellowblazing: Taking a road to bypass trail (yellow refers to the painted center line)
Brain: The top lid of a pack.
Bounce Box: A resupply package mailed ahead for a thru-hiker to pick up at a given destination.
Cathole: A self-dug hole to defecate into.
Circle of Death: Passing around the pot of leftover food to avoid having to pack it out.
Contouring: Known as “sidling” in New Zealand and "traversing" elsewhere, this is walking across a slope, perpendicular to the fall-line, while staying at the same elevation the whole way.
Cowboy Coffee: A rough and rugged drink in which coffee grounds are heated in a pot with boiling water. After the grounds settle, the water is syphoned off without filtration.
Crotch Rot: The unfortunate result of too many days in the same undies.
Ditty Bag: A small water-resistant bag to carry your personal effects.
Fastpacking: The ultimate in ultra-light obsessiveness, this term refers to those hikers who not only cut weight but also try to cover as much distance as possible in as little time as possible. Fastpackers will often run sections of the trail.
Glamping: The act of sleeping in luxurious tents or canopies equipped with heat, electricity, and other amenities. The less said about this, the better.
GORP: Acronym for "Good Old Raisins and Peanuts,” often used as general shorthand for basic trail mix. To a lesser extent some interpret the acronym as “Gobs Of Raw Protein" instead.
Hiker Tan: A sheen of dirt and mud accumulated from the trail, a.k.a. the kind of tan that washes off.
HYOH: Acronym for "hike your own hike." Often used as a subtle suggestion for other hikers to get lost.
Leave No Trace (LNT): The philosophy and practice of minimizing human impact on the environment.
NoBo & SoBo: Northbound and Southbound, respectively. Used by thru-hikers to quickly describe which direction he/she is hiking on a long trail.
Peak-bagging: The pursuit of summiting as many different peaks as possible.
Postholing: The deep holes that one's legs make when attempting to cross a snowfield without snowshoes.
Scamping: Camping in a spot that may or may not be illegal to use, akin to squatting.
See-far: You see something far, and you walk to it. Example: always go at least two see-fars from camp to dig a cathole.
Slackpacking: The slack a backpack has when not fully packed. Slackpackers are enamored with the idea of ultralight, so much so that you may catch them counting grams under their breath.
Springer Fever: The phenomenon that occurs when the sun finally makes an appearance after a long winter and hikers start itching for the trail.
Topo: Short for “topographical map”, the only kind worth carrying,
Triple Crown: The completion of all three major United States long trails: the Appalachian Trail, Continental Divide Trail, and Pacific Crest Trail. A highly respected and coveted accomplishment.
Turtleing: Fallying backwards with your pack on and not being able to get up.
Vitamin I: Ibuprofen. Often used liberally by backpackers.
Yogi-ing: Takes its name from Yogi Bear and refers to the subtle hints (or sometimes blatant references) that a hiker might make in order to get food or other useful things for free.
Yo-Yo: In thru-hiker lingo, this is a person who has hiked a long trail, then turned around and hiked it again in the opposite direction.
Zero Day: A rest day in which a backpacker hikes zero miles. As in, “Take that zero day. You deserve it.”