Glossary

Acclimatization, The body’s gradual adjustment to high altitude’s thinner air, achieved by ascending slowly. Prevents altitude sickness. (Ch. 22)

Acute mountain sickness (AMS), The common, mild form of altitude illness: headache, nausea, fatigue, and poor sleep from ascending too fast. (Ch. 22)

Base layer, The clothing layer worn against the skin, made of wicking synthetic or wool, that moves sweat away from the body. (Ch. 2)

Base weight, The weight of your pack and gear excluding consumables (food, water, fuel); the number used to compare and lighten a kit. (Ch. 15)

Bear canister, A hard-sided, bear-proof container for food and scented items, required in many areas and the most reliable food-storage method. (Ch. 23)

Bear hang, Suspending a food bag from a tree branch, out of a bear’s reach, where canisters aren’t required; harder to do well than it looks. (Ch. 23)

Bivy (bivy sack), A minimal waterproof shelter that wraps around your sleeping bag; the lightest, smallest shelter option. (Ch. 9)

Bonk, A sudden energy crash from running low on fuel; prevented by grazing steadily. (Ch. 19)

Cathole, A small hole, 6–8 inches (15–20 cm) deep and 200 feet from water, dug to bury human solid waste. (Ch. 20)

Cold-soaking, Rehydrating food in cold water over a few hours instead of cooking it, the core no-stove meal method. (Ch. 19)

Contour lines, Lines on a topographic map connecting points of equal elevation; bunched lines mean steep terrain, spread lines mean gentle. (Ch. 16)

Declination, The difference between true north (maps) and magnetic north (compass needle); must be accounted for in accurate compass work. (Ch. 16)

Down, Bird-plumage insulation with the best warmth-for-weight and packability, but which loses insulation when wet. (Ch. 7)

Fill power, A measure of down quality (loft per ounce); higher fill power means lighter for the same warmth, not warmer. (Ch. 7)

Footprint, A ground sheet cut to a tent’s shape that protects the floor from abrasion; must not extend past the tent’s edges. (Ch. 9)

Freestanding tent, A tent that stands on its poles without stakes; the easiest type for beginners. (Ch. 9)

Giardia, A waterborne protozoan parasite causing severe gastrointestinal illness; the most common backcountry water hazard. (Ch. 11)

HACE / HAPE, High-altitude cerebral edema (brain swelling) and high-altitude pulmonary edema (lung fluid): rare, deadly altitude illnesses requiring immediate descent. (Ch. 22)

Hot spot, An early, tender warning point on the foot that precedes a blister; treat within five minutes. (Ch. 5)

Hypothermia, A dangerous drop in core body temperature, the deadliest common hiking hazard; occurs in cool, wet, windy conditions, not only winter. (Ch. 22)

Internal frame, A backpack with supporting stays built inside, holding the load close to the back for balance; the modern standard. (Ch. 6)

Leave No Trace (LNT), The seven-principle outdoor ethic for minimizing impact so wild places stay healthy. (Ch. 21)

Loft, A sleeping bag or insulation’s ability to fluff up and trap warm air; destroyed by long compression. (Ch. 7)

Midlayer, The insulating clothing layer (fleece or puffy) worn between the base layer and shell. (Ch. 2)

Moleskin, Soft padded adhesive felt used to cushion hot spots and, cut as a donut, to relieve pressure on a blister. (Ch. 5)

Mummy bag, A tapered, hooded sleeping bag that minimizes dead air space to conserve warmth; the backpacking standard. (Ch. 7)

Naismith’s rule, A pace estimate: about 1 hour per 3 miles (5 km) plus 30 minutes per 1,000 feet (300 m) of climbing. (Ch. 1)

Permethrin, An insect treatment applied to clothing (not skin) that kills ticks on contact. (Ch. 23)

Personal locator beacon (PLB), A subscription-free device that broadcasts an emergency SOS with your location to rescue authorities. (Ch. 16)

Rest step, A climbing technique of briefly locking the rear leg each stride so the skeleton bears weight, allowing steady ascent without stopping. (Ch. 17)

R-value, A standardized, additive measure of a sleeping pad’s insulation from the ground; higher is warmer. (Ch. 8)

Satellite messenger, A subscription device that sends texts and an SOS via satellite from beyond cell coverage. (Ch. 16)

Shell, The outer, wind- and waterproof clothing layer worn over insulation. (Ch. 2)

Switchbacks, Zig-zagging trail segments that ease the grade of a steep climb; never cut across them (it causes erosion). (Ch. 21)

Ten Essentials, The standard checklist of survival systems (navigation, headlamp, sun protection, first aid, knife, fire, shelter, extra food, water, clothes). (Ch. 4)

Three-season tent, A tent built for spring, summer, and fall; the right choice for nearly all backpacking. (Ch. 9)

Topographic (topo) map, A map showing terrain shape through contour lines of elevation. (Ch. 16)

Torso length, The measurement (neck’s C7 vertebra to the top of the hips) that sizes a backpack, not your height. (Ch. 6)

Trailhead, The point where a trail begins, typically off a road with parking. (Ch. 1)

Treeline, The elevation above which trees no longer grow; above it, exposure to weather and lightning increases. (Ch. 22)

Umbles, The early warning signs of hypothermia: st-umbling, m-umbling, f-umbling, gr-umbling. (Ch. 22)

Urushiol, The oil in poison ivy, oak, and sumac that causes their itchy rash; wash it off skin and gear promptly. (Ch. 23)

WAG bag, A chemical waste bag for packing out human solid waste where catholes are prohibited. (Ch. 20)

Wicking, Fabric’s ability to move moisture (sweat) away from the skin to evaporate; the job of a base layer. (Ch. 2)