Definition of "Fast" :
noun: abstaining from food
verb: abstain from eating
"Before the medical exam, you must fast."
verb: abstain from certain foods, as for religious or medical reasons
"Catholics sometimes fast during Lent."
adjective: (of a photographic lens or emulsion) causing a shortening of exposure time
"A fast lens."
adjective: unwavering in devotion to friend or vow or cause
adjective: acting or moving or capable of acting or moving quickly
adjective: at a rapid tempo
"The band played a fast fox trot."
adjective: (used of timepieces) indicating a time ahead of or later than the correct time
"My watch is fast."
adjective: securely fixed in place
adjective: hurried and brief
"A fast visit."
adjective: unrestrained by convention or morality
adjective: resistant to destruction or fading
adjective: (of surfaces) conducive to rapid speeds
"A fast road."
adverb: quickly or rapidly (often used as a combining form)
"How fast can he get here?."
adverb: firmly or closely
"Held fast to the rope."