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1. To separate some material, such as chaff, from grain by means of a current of air: The farmer winnows out the chaff with a machine. There is always some debris in the harvest, but we winnow it out.
2. To separate or get rid of some unfit or undesirable part; eliminate something or someone: The lions tend to winnow out the sick antelope. The political process will winnow the weakest candidates out.
3. To sort or select some fit or desirable part; extract someone or something: We winnowed out the top candidates from the rest and interviewed them. There are only a few good pieces of wood in this shipment, and it will take a long time to winnow them out.
4. To rid some group of unfit or undesirable members: The test winnowed out the applicant pool.