1. To use a current of air to blow chaff away from grain. A noun or pronoun can be used between "winnow" and "away." The revolutionary new machine promises to winnow away chaff much faster with a lower percentage of grain being lost or destroyed in the process. Before they had mechanical means, farmers had to rely on the wind to winnow chaff and other debris away.

2. To filter out and remove persons or things that are unfit, unwanted, or unreliable. A noun or pronoun can be used between "winnow" and "away." The grueling nature of these exams in meant to test the learning of up-and-coming doctors, as well as winnow away those who don't have the determination and resilience. The committee will first winnow the weakest applicants away before beginning to seriously examine those who might be accepted into the university. We'll subject your thesis to a panel of professors in order to winnow away any problems with logic or evidence.

3. To cause a group to become smaller by removing the least able or desirable people or things from it. A noun or pronoun can be used between "winnow" and "away." The company always takes on a large number of interns each summer, winnowing it away until only the most capable remain to be given work full time. Natural selection winnows out the population of animals, leaving behind those with the traits necessary to withstand the environment and its predators.