win·now 
(wĭnō)
(wĭnō)v. win·nowed, win·now·ing, win·nows
v.tr.
1. To separate the chaff from (grain) by means of a current of air.
2. To blow (chaff) off or away.
3. To examine closely in order to separate the good from the bad; sift: The judges winnowed a thousand essays down to six finalists.
4.
a. To separate or get rid of (an undesirable part); eliminate: winnowing out the errors in logic.
b. To sort or select (a desirable part); extract: The investigators winnowed the facts from the testimony.
5. To blow on; fan: a breeze winnowing the tall grass.
v.intr.
1. To separate grain from chaff.
2. To separate the good from the bad.
n.
1. A device for winnowing grain.
2. An act of winnowing.
[Middle English winnewen, alteration of windwen, from Old English windwian, from wind, wind; see WIND1.]
winnow·er n.