any abnormal phenomenon or product or unusual object; anomaly; aberration.

a person or animal on exhibition as an example of a strange deviation from nature; monster.

a sudden and apparently causeless change or turn of events, the mind, etc.; an apparently capricious notion, occurrence, etc.

That kind of sudden storm is a freak.

Numismatics . an imperfect coin, undetected at the mint and put into circulation.

Philately . a stamp differing from others of the same printing because of creases, dirty engraving plates, etc. Compare error ( def. 8 ) , variety ( def. 8 ) .

Slang .

a person who has withdrawn from normal, rational behavior and activities to pursue one interest or obsession

a drug freak.

a devoted fan or follower; enthusiast

a baseball freak.

a hippie.

Archaic . capriciousness; whimsicality.

unusual; odd; irregular

a freak epidemic.

to become or make frightened, nervous, or wildly excited

The loud noise caused the horse to freak.

freak out, Slang .

to enter into or cause a period of irrational behavior or emotional instability, as under the influence of a drug

to be freaked out on LSD.

to lose or cause to lose emotional control from extreme excitement, shock, fear, joy, despair, etc.

Seeing the dead body freaked him out.

noun

normality , ordinary , regular , commonality , regularity

noun

aberration , abortion , anomaly , chimera , curiosity , geek * , grotesque , malformation , miscreation , misshape , monster , monstrosity , mutant , mutation , oddity , queer , rarity , sport , weirdo * , caprice , conceit , crochet , fad , fancy , folly , humor , megrim , quirk , turn , twist , vagary , whimsy , addict , aficionado , buff , bug * , devotee , enthusiast , fan , fanatic , fiend * , maniac , nut * , zealot , bug , bee , boutade , impulse , notion , whim , bizarre , capriccio , crotchet , eccentric , fiend , fleck , flimflam , frolic , geek , lusus naturae , prank , rave , whimsey , whimsicality

verb

flip out * , go beserk , go insane , go mad , lose control , rave , unhinge * , wig out *