Source : Webster's Revised Unabridged Dictionary (1913)

Winnowing \Win"now*ing\, n.
   The act of one who, or that which, winnows.

Winnew \Win"new\, v. t. [imp. & p. p. {Winnowed}; p. pr. & vb.
   n. {Winnowing}.] [OE. windewen, winewen, AS. windwian; akin
   to Goth. winpjan (in comp.), winpi-skauro a fan, L. ventilare
   to fan, to winnow; cf. L. wannus a fan for winnowing, G.
   wanne, OHG. wanna. ????. See {Wind} moving air, and cf.
   {Fan}., n., {Ventilate}.]
   1. To separate, and drive off, the chaff from by means of
      wind; to fan; as, to winnow grain.

            Ho winnoweth barley to-night in the threshing floor.
                                                  --Ruth. iii.
                                                  2.

   2. To sift, as for the purpose of separating falsehood from
      truth; to separate, as had from good.

            Winnow well this thought, and you shall find This
            light as chaff that flies before the wind. --Dryden.

   3. To beat with wings, or as with wings.[Poetic]

            Now on the polar winds; then with quick fan Winnows
            the buxom air.                        --Milton.

Source : WordNet®

winnowing
     n : the act of separating grain from chaff; "the winnowing was
         done by women" [syn: {winnow}, {sifting}]