Source : Webster's Revised Unabridged Dictionary (1913)

Riddle \Rid"dle\, v. t. [imp. & p. p. {Riddled}; p. pr. & vb. n.
   {Riddling}.]
   1. To separate, as grain from the chaff, with a riddle; to
      pass through a riddle; as, riddle wheat; to riddle coal or
      gravel.

   2. To perforate so as to make like a riddle; to make many
      holes in; as, a house riddled with shot.

Riddle \Rid"dle\, n. [For riddels, s being misunderstood as the
   plural ending; OE. ridels, redels. AS. r?dels; akin to D.
   raadsel, G. r["a]thsel; fr. AS. r?dan to counsel or advise,
   also, to guess. [root]116. Cf. {Read}.]
   Something proposed to be solved by guessing or conjecture; a
   puzzling question; an ambiguous proposition; an enigma;
   hence, anything ambiguous or puzzling.

         To wring from me, and tell to them, my secret, That
         solved the riddle which I had proposed.  --Milton.

         'T was a strange riddle of a lady.       --Hudibras.

Riddle \Rid"dle\, n. [OE. ridil, AS. hridder; akin to G. reiter,
   L. cribrum, and to Gr. ??? to distinguish, separate, and G.
   rein clean. See {Crisis}, {Certain}.]
   1. A sieve with coarse meshes, usually of wire, for
      separating coarser materials from finer, as chaff from
      grain, cinders from ashes, or gravel from sand.

   2. A board having a row of pins, set zigzag, between which
      wire is drawn to straighten it.

Riddle \Rid"dle\, v. t.
   To explain; to solve; to unriddle.

         Riddle me this, and guess him if you can. --Dryden.

Riddle \Rid"dle\, v. i.
   To speak ambiguously or enigmatically. ``Lysander riddels
   very prettily.'' --Shak.

Source : WordNet®

riddle
     n 1: a difficult problem [syn: {conundrum}, {enigma}, {brain-teaser}]
     2: a coarse sieve (as for gravel)
     v 1: pierce many times; "The bullets riddled his body"
     2: set a difficult problem or riddle; "riddle me a riddle"
     3: separate with a riddle, as grain from chaff [syn: {screen}]
     4: speak in riddles
     5: explain a riddle