Crawl means to move forward on your hands and knees, the way babies do before they learn to walk. When you crawl under a fence or through a tunnel, you're pulling yourself along close to the ground. Soldiers might crawl on their bellies to stay hidden, and toddlers crawl across the living room floor as they explore their world.

The word also describes any slow, difficult movement. Traffic crawls during rush hour, barely inching forward. Time seems to crawl when you're waiting for something exciting, like your birthday or the last day of school. A movie that makes you restless might feel like it's crawling along.

When something makes your skin crawl, it gives you an uncomfortable, creepy feeling, like when you see a spider or hear fingernails scraping across a chalkboard. The phrase captures that squirmy sensation of wanting to get away from something unpleasant.

As a noun, in swimming, the crawl (or freestyle) is the fastest stroke, where you pull one arm forward at a time while kicking your legs and turning your head to breathe. Despite its name, swimmers using the crawl stroke move through water quickly and smoothly.