fast (Noun) — Abstaining from food.
fast (Verb) — Abstain from certain foods, as for religious or medical reasons. ex. "Catholics sometimes fast during Lent"
fast (Verb) — Abstain from eating. ex. "Before the medical exam, you must fast"
fast (Adjective) — Acting or moving or capable of acting or moving quickly. ex. "fast film" ex. "on the fast track in school" ex. "set a fast pace" ex. "a fast car"
fast (Adjective) — (used of timepieces) indicating a time ahead of or later than the correct time. ex. "my watch is fast"
fast (Adjective) — (music) at a rapid tempo. ex. "the band played a fast fox trot"
fast (Adjective) — (of surfaces) conducive to rapid speeds. ex. "a fast road" ex. "grass courts are faster than clay"
fast (Adjective) — Resistant to destruction or fading. ex. "fast colours"
fast (Adjective) — Unrestrained by convention or morality. ex. "fast women"
fast (Adjective) — Hurried and brief. ex. "a fast visit"
fast (Adjective) — Securely fixed in place.
fast (Adjective) — Unwavering in devotion to friend, vow or cause. ex. "fast friends"
fast (Adjective) — (of a photographic lens or emulsion) causing a shortening of exposure time. ex. "a fast lens"
fast (Adverb) — Quickly or rapidly (often used as a combining form). ex. "how fast can he get here?" ex. "ran as fast as he could" ex. "needs medical help fast" ex. "fast-running rivers" ex. "fast-breaking news" ex. "fast-opening (or fast-closing) shutters"
fast (Adverb) — Firmly or closely. ex. "held fast to the rope" ex. "her foot was stuck fast"