To expose (grain or other substances) to the wind or to a current of air so that the lighter particles (as chaff or other refuse matter) are separated or blown away; to clear of refuse material by this method. To subject to a process likened to the winnowing of grain, in order to separate the various parts or elements, esp. the good from the bad; hence, to clear of worthless or inferior elements. To separate or drive off (lighter or refuse particles); fig. to separate (the worthless part from the valuable); to get rid of, clear away, eliminate (something undesirable).