THESAURUS
unsturdy
abortive, bootless, crumbling, decrepit, disintegrating, failed, failing, fruitless, futile, ineffective, ineffectual, inefficacious, infirm, lame, manque, miscarried, miscarrying, of no effect, poor, poorish, rotten, rotten at, stickit, stillborn, successless, unfirm, unfortunate, unsolid, unsound, unstable, unsubstantial, unsuccessful, useless