A dart is a tiny missile with a pointy end that can be a weapon or part of a game, like those pointy things that people throw at dartboards. If a person darts, it just means she’s moving quickly.
A dart can be thrown or fired by blowing through a contraption, like when people who study big animals shoot a tranquilizer dart at a lion so they can put it to sleep without getting close. Darts can be weapons or part of a game often found in bars. Just as a dart moves quickly, a person can dart if they move quickly. Bees tend to dart around in the air. In football, a quick running back darts to avoid defenders