Source : Webster's Revised Unabridged Dictionary (1913)

Freak \Freak\ (fr[=e]k), v. t. [imp. & p. p. {Freaked}
   (fr[=e]kt); p. pr. & vb. n. {Freaking}.] [Akin to OE. frakin,
   freken, freckle, Icel. freknur, pl., Sw. fr["a]kne, Dan.
   fregne, Gr. perkno`s dark-colored, Skr. p[.r][,c]ni
   variegated. Cf. {Freckle}, {Freck}.]
   To variegate; to checker; to streak. [R.]

         Freaked with many a mingled hue.         --Thomson.

Freak \Freak\, n. [Prob. from OE. frek bold, AS. frec bold,
   greedly; akin to OHG. freh greedly, G. frech insolent, Icel.
   frekr greedy, Goth. fa['i]hufriks avaricious.]
   A sudden causeless change or turn of the mind; a whim of
   fancy; a capricious prank; a vagary or caprice.

         She is restless and peevish, and sometimes in a freak
         will instantly change her habitation.    --Spectator.

   Syn: Whim; caprice; folly; sport. See {Whim}.

Source : WordNet®

freak
     n 1: a person or animal that is markedly unusual or deformed
          [syn: {monster}, {monstrosity}, {lusus naturae}]
     2: someone who is so ardently devoted to something that it
        resembles an addiction; "a golf addict"; "a car nut"; "a
        news junkie" [syn: {addict}, {nut}, {junkie}, {junky}]

freak
     v : lose one's nerve; "When he saw the accident, he freaked out"
         [syn: {freak out}, {gross out}]