To remove chaff from grain by blowing air on it. Farmers winnow the harvested wheat to separate the grain from the chaff.
To examine and remove the bad or unnecessary parts of something. The editor winnowed the manuscript to improve its clarity and focus.
To reduce a large number of people or things to a smaller number by judging their quality. The competition winnowed the applicants down to the most qualified candidates.
To move lightly or be driven by the wind; to drift or flutter through the air. Dry leaves winnowed along the sidewalk in the autumn breeze.