Collins COBUILD Advanced Learner's English Dictionary - winnow out

If you winnow out part of a group of things or people, you identify the part that is not useful or relevant and the part that is. (WRITTEN) The committee will need to winnow out the nonsense and produce more practical proposals if it is to achieve results... Time has winnowed out certain of the essays as superior. PHRASAL VERB: V P n (not pron), V P n (not pron)