Windproof describes something designed to block wind from passing through it. A windproof jacket keeps cold air from cutting through the fabric and chilling your body, even when you're standing in a strong breeze. The material is woven tightly enough, or coated specially, so wind can't sneak through the tiny gaps between fibers.

This matters more than you might think. Regular fabric, even if it's thick, can let wind pass right through. You've probably felt this on a cold, windy day: your sweater feels warm indoors, but outside the wind goes straight through it, making you shiver. A windproof layer stops that from happening.

Windproof gear is essential for activities like hiking, skiing, or cycling, where you're exposed to wind for long periods. Campers prize windproof tents that won't flap wildly or let drafts in during storms. Mountain climbers rely on windproof clothing because at high altitudes, even a moderate wind can be dangerous.

The word can describe any object designed to resist wind: windproof matches stay lit in a breeze, windproof umbrellas resist turning inside out, and windproof lighters keep working when regular ones fail.