adj. 25B6; adjective
it was useless to try 007C; a piece of useless knowledge : FUTILE, to no avail, in vain, vain, pointless, to no purpose, unavailing, hopeless, ineffectual, ineffective, to no effect, fruitless, unprofitable, profitless, unproductive; broken, kaput; archaic bootless.
(informal) he was useless at his job : INCOMPETENT, inept, ineffective, incapable, inadequate, hopeless, bad; informal pathetic, a dead loss.
useful, beneficial, competent.