Real Dictionary

fast
adjective: Fast means happening, moving, or doing something at great speed. You also use fast in questions or statements about speed.

fast in American English 1
not easily moved, freed, or separated; firm, fixed, or stuck
adjective: moving or able to move, operate, function, or take effect quickly; quick; swift; rapid

fast in American English 2
the act of fasting
to abstain from all or certain foods, as in observing a holy day
intransitive verb: to abstain from all food
noun: an abstinence from food, or a limiting of one's food, esp. when voluntary and as a religious observance; fasting
transitive verb: to cause to abstain entirely from or limit food; put on a fast

fast in American English 3
noun: a chain or rope for mooring a vessel

FAST in British English
acronym for: face, arms, speech, time: used to assess whether a person has suffered a stroke

fast in British English 1
adjective: acting or moving or capable of acting or moving quickly; swift

fast in British English 2
noun: an act or period of fasting
verb: to abstain from eating all or certain foods or meals, esp as a religious observance