winnow

Short definition from Wiktionary

Verb

1. 1
   To subject (granular material, especially food grain) to a current of air separating heavier and lighter components, as grain from chaff.
2. 2
   To separate, sift, analyse, or test by separating items having different values.
3. 3
   To blow upon or toss about by blowing; to set in motion as with a fan or wings.
4. 4
   To move about with a flapping motion, as of wings; to flutter.

Noun

1. 1
   That which winnows or which is used in winnowing; a contrivance for fanning or winnowing grain.
2. 2
   The act of winnowing