WordNet sense 1 (serving no useful purpose; having no excuse for being):

pointless, superfluous, wasted

WordNet sense 2 (lacking in usefulness or value):

worthless

WordNet sense 3 (producing no result or effect):

futile, ineffectual, unavailing

WordNet sense 4 (having no beneficial use or incapable of functioning usefully):

useless

WordNet sense 5 (disinclined to work or exertion):

faineant, indolent, lazy, slothful, work-shy

WordNet sense 6 (not in action or at work):

idle