fast - [fast, fahst] adjective, fast·er, fast·est, adverb, fast·er, fast·est, noun
1. moving or able to move, operate, function, or take effect quickly; quick; swift; rapid: a fast horse; a fast pain reliever; a fast thinker.
2. done in comparatively little time; taking a comparatively short time: a fast race; fast work.
3. (of time) indicating a time in advance of the correct time, as of a clock.