One who is deficient in judgment, sense, or understanding.
One who acts unwisely on a given occasion: I was a fool to have quit my job.
One who has been tricked or made to appear ridiculous; a dupe: They made a fool of me by pretending I had won.
Informal A person with a talent or enthusiasm for a certain activity: a dancing fool; a fool for skiing.
A member of a royal or noble household who provided entertainment, as with jokes or antics; a jester.
One who subverts convention or orthodoxy or varies from social conformity in order to reveal spiritual or moral truth: a holy fool.
A dessert made of stewed or puréed fruit mixed with cream or custard and served cold.
Archaic A mentally deficient person; an idiot.
v.
fooled, fool·ing, fools
v.
tr.
To deceive or trick; dupe: "trying to learn how to fool a trout with a little bit of floating fur and feather"(Charles Kuralt).
To confound or prove wrong; surprise, especially pleasantly: We were sure they would fail, but they fooled us.
v.
intr.
Informal
To speak or act facetiously or in jest; joke: I was just fooling when I said I had to leave.
To behave comically; clown.
To feign; pretend: He said he had a toothache but he was only fooling.
To engage in idle or frivolous activity.
To toy, tinker, or mess: shouldn't fool with matches.
adj.
Informal
Foolish; stupid: off on some fool errand or other.
Phrasal Verbs:
fool aroundInformal
To engage in idle or casual activity; putter: was fooling around with the old car in hopes of fixing it.
To engage in frivolous activity; make fun.
To engage in casual, often promiscuous sexual acts.
Phrasal Verb(s): fool around Informal
To engage in idle or casual activity; putter: was fooling around with the old car in hopes of fixing it.
To engage in frivolous activity; make fun.
To engage in casual, often promiscuous sexual acts.
fool awayTo waste (time or money) foolishly; squander: fooled away the week's pay on Friday night.
Idiom(s):
play/act the fool
To act in an irresponsible or foolish manner.
To behave in a playful or comical manner.
[Middle English fol, from Old French, from Late Latin follis, windbag, fool, from Latin follis, bellows; see bhel-2 in Indo-European roots.]
Word History: The pejorative nature of the term fool is strengthened by a knowledge of its etymology. Its source, the Latin word follis, meant "a bag or sack, a large inflated ball, a pair of bellows." Users of the word in Late Latin, however, saw a resemblance between the bellows or the inflated ball and a person who was what we would call "a windbag" or "an airhead." The word, which passed into English by way of French, is first recorded in English in a work written around the beginning of the 13th century with the sense "a foolish, stupid, or ignorant person."
[fool] 
