1. To use a current of wind or air to separate grain from chaff. A noun or pronoun, especially "grain," is used between "winnow" and "from." The revolutionary new machine promises to winnow grain from chaff much more efficiently. Before they had mechanical means, farmers had to rely on the wind to winnow chaff and other debris away.

2. To select the most capable, desirable, or viable persons or things from a group, discarding the rest. A noun or pronoun is used between "winnow" and "from." The grueling nature of these exams in meant to winnow the best or most serious medical students from those who don't have what it takes to succeed. The committee will winnow the strongest applications from weakest.