adj. 1 excessively proud or conceited, esp. about one's own attributes. 2 empty, trivial, unsubstantial (vain boasts; vain triumphs). 3 useless; followed by no good result (in the vain hope of dissuading them). in vain without result or success (it was in vain that we protested). take a person's name in vain use it lightly or profanely. vainly adv. vainness n.
[ ME f. OF f. L vanus empty, without substance ]