plow under transitive verb 1. a.: to cover a green manure crop, crop residues, or barnyard manure by plowing b.: to plow a field of a growing unharvested crop 2.: to cause to disappear : bury, overwhelm < let us not plow under the family farmer — A.E.Stevenson b.1900 > < talented students … were too often plowed under — E.A.Weeks >