The process of hurling threshed grain into the air with a kind of fan; the wind separated the valuable grain from the chaff (Ruth 3: 2) so that it could be stored. It was John the Baptist's metaphor for the divine judgement (Luke 3: 17).
Citation for winnowing
Citation styles are based on the Chicago Manual of Style, 15th Ed., and the MLA Style Manual, 2nd Ed..
MLA
"winnowing." In A Dictionary of the Bible. Ed. W. R. F. Browning. Oxford Biblical Studies Online. May 22, 2013. <http://www.oxfordbiblicalcstudies.com/article/opr/t94/e2043>.
Chicago
"winnowing." In A Dictionary of the Bible. , edited by W. R. F. Browning. Oxford Biblical Studies Online, http://www.oxfordbiblicalcstudies.com/article/opr/t94/e2043 (accessed May 22, 2013).