winnow

noun

That which winnows or which is used in winnowing; a contrivance for fanning or winnowing grain.

1. To subject (granular material, especially food grain) to a current of air separating heavier and lighter components, as grain from chaff.
2. To separate, sift, analyze, or test by separating items having different values.

   They winnowed the field to twelve.

3. To blow upon or toss about by blowing; to set in motion as with a fan or wings.
4. To move about with a flapping motion, as of wings; to flutter.