v. blow away; separate good parts from bad; sort or select desirable; extract
This test will winnow out the students who study from those who don't bother.
Sentence in Classic:
These I heated before the fire, as well as I could, and rubbed them till the husks came off, which I made a shift to winnow from the grain.
Gulliver's Travels(V2) By Jonathan Swift Context
A wayfarer will meet you and will say it must be a winnowing shovel that you have got upon your shoulder; on this you must fix the oar in the ground and sacrifice a ram, a bull, and a boar to Neptune.