Definitions of winnow:

• noun:   the act of separating grain from chaff

  Example: "The winnowing was done by women"

• verb:   treat by exposure to a current of air so that waste matter is eliminated

  Example: "Winnow grain"

• verb:   separate from chaff

  Example: "She stood there winnowing grain all day in the field"

• verb:   remove by a current of air

  Example: "Winnow chaff"

• verb:   blow on

  Example: "The wind was winnowing her hair"