Source : Webster's Revised Unabridged Dictionary (1913)

Harlequin \Har"le*quin\, n. [F. arlequin,formerly written also
   harlequin (cf. It, arlecchino), prob. fr. OF. hierlekin,
   hellequin, goblin, elf, which is prob. of German or Dutch
   origin; cf. D. hel hell. Cf. {Hell}, {Kin}.]
   A buffoon, dressed in party-colored clothes, who plays
   tricks, often without speaking, to divert the bystanders or
   an audience; a merry-andrew; originally, a droll rogue of
   Italian comedy. --Percy Smith.

         As dumb harlequin is exhibited in our theaters.
                                                  --Johnson.

   {Harlequin bat} (Zo["o]l.), an Indian bat ({Scotophilus
      ornatus}), curiously variegated with white spots.

   {Harlequin beetle} (Zo["o]l.), a very large South American
      beetle ({Acrocinus longimanus}) having very long legs and
      antenn[ae]. The elytra are curiously marked with red,
      black, and gray.

   {Harlequin cabbage bug}. (Zo["o]l.) See {Calicoback}.

   {Harlequin caterpillar}. (Zo["o]l.), the larva of an American
      bombycid moth {(Euch[ae]tes egle)} which is covered with
      black, white, yellow, and orange tufts of hair.

   {Harlequin duck} (Zo["o]l.), a North American duck
      ({Histrionicus histrionicus}). The male is dark ash,
      curiously streaked with white.

   {Harlequin moth}. (Zo["o]l.) See {Magpie Moth}.

   {Harlequin opal}. See {Opal}.

   {Harlequin snake} (Zo["o]l.), a small, poisonous snake
      ({Elaps fulvius}), ringed with red and black, found in the
      Southern United States.

Harlequin \Har"le*quin\, n. i.
   To play the droll; to make sport by playing ludicrous tricks.

Harlequin \Har"le*quin\, v. t.
   Toremove or conjure away, as by a harlequin's trick.

         And kitten,if the humor hit Has harlequined away the
         fit.                                     --M. Green.

Source : WordNet®

harlequin
     n : a clown or buffoon (after the Harlequin character in the
         commedia dell'arte)

harlequin
     v : variegate with spots or marks; "His face was harlequined
         with patches"