Source : Webster's Revised Unabridged Dictionary (1913)

Winnow \Win"now\, v. i.
   To separate chaff from grain.

         Winnow not with every wind.              --Ecclus. v.
                                                  9.

Source : WordNet®

winnow
     n : the act of separating grain from chaff; "the winnowing was
         done by women" [syn: {winnowing}, {sifting}]
     v 1: separate from chaff; "She stood there winnowing grain all
          day in the field" [syn: {fan}]
     2: blow on; "The wind was winnowing her hair"
     3: treat by exposure to a current of air so that waste matter
        is eliminated; "winnow grain"
     4: remove by a current of air; "winnow chaff"