fast

Fast describes someone or something that moves quickly, is not easily moved or is firmly shut. (adjective)

Fast means swiftly or ahead of time. (adverb)

Fast means to eat little or no food. (verb)

An example of fast is not eating for twelve hours before having blood drawn.

A fast is a period of time during which you go without food. (noun)

An example of fast is not eating during daylight hours for Ramadan.

See fast in Webster's New World College Dictionary

adjective

not easily moved, freed, or separated; firm, fixed, or stuck: the ship was fast on the rocks
firmly fastened or shut: make the shutters fast
loyal; devoted: fast friends
that will not fade: fast colors
rapid in movement or action; swift; quick; speedy
permitting or facilitating swift movement: a fast highway
taking or lasting a short time: a fast lunch
showing or keeping to a time in advance of a standard or scheduled time: his watch is fast
1. living in a reckless, wild, dissipated way: a fast crowd
2. promiscuous sexually
☆ Informal glib and deceptive: a fast talker
Slang acting, gotten, done, etc. quickly and often dishonestly: out for a fast buck
Bacteriology resistant to dissolution or decolorization, as certain bacteria
Photog. adapted to or allowing very short exposure time: a fast lens, fast film
Now Dial. complete; sound: a fast sleep

adverb

noun

Naut. a rope for mooring: a stern fast

intransitive verb

noun

See fast in American Heritage Dictionary 4

(făst)

adjective fast·er, fast·est

Acting, moving, or capable of acting or moving quickly; swift.
a. Accomplished in relatively little time: a fast visit.
b. Acquired quickly with little effort and sometimes unscrupulously: made a fast buck scalping tickets.
Quick to understand or learn; mentally agile: a class for the faster students.
Indicating a time somewhat ahead of the actual time: The clock is fast.
Allowing rapid movement or action: a fast running track.
Designed for or compatible with a short exposure time: fast film.
a. Disposed to dissipation; wild: ran with a fast crowd.
b. Flouting conventional moral standards; sexually promiscuous.
Resistant, as to destruction or fading: fast colors.
Firmly fixed or fastened: a fast grip.
Fixed firmly in place; secure: shutters that are fast against the rain.
Firm in loyalty: fast friends.
Lasting; permanent: fast rules and regulations.
Deep; sound: in a fast sleep.