Synonyms to tilt at windmills

labor in vain, be found wanting, be unsuccessful, beat the air, bootless errand, come to grief, fail, fail of success, flunk, flunk out, go bankrupt, labor of Sisyphus, lash the waves, lose, lost, milk the ram, not come off, not pass, not work, snipe hunt, sow the sand, waste of breath, waste of labor, waste of time, wild-goose chase, work of Penelope