If you were the first one to reach the finish line in gym class, the coach might have called you swift. Swift means quick or fast-moving. A glance, a current, even a decision can be swift.
You can use the adjective swift to describe things that move or happen rapidly and smoothly. Deciding to borrow a parent's car without permission could result in swift punishment. Foxes are so swift that if you leave the chicken coop open for a moment, one might slip in. Conversely, if innuendo sails over your head, your friends might say, “You’re not too swift on the uptake, are you?” A swift is also a small bird that looks a lot like a swallow.