Thesaurus

adynamic, anaemic, anemic, anserine, anthropoid, anthropomorphic, anthropomorphous, artless, asthenic, audible, behind, blockheaded, boneheaded, botched, botchy, breakable, bungled, bungling, butcherly, cloddish, clumsy, crude, cut, daily, dainty, day-after-day, day-to-day, debile, debilitated, decrepit, delicate, dense, descending, detectable, dilute, diluted, dim, discernible, doltish, dopey, dopy, down, downbound, downcast, downfield, downward, dull, dumb, earthborn, enervated, errant, erring, error-prone, ethereal, every day, exquisite, faint, fallen, fallible, fatheaded, feeble, feminine, first-string, flaccid, flimsy, foolish, fragile, frail, fumbling, gaumless, gooselike, goosey, goosy, gormless, gossamer, gutless, half-hardy, hearable, helpless, hominal, hominian, hominid, hominine, hopeless, human, humanlike, humble, imperfect, impotent, incapacitated, incompetent, ineffective, ineffectual, inexperienced, inexperient, infirm, jerky, jerry-built, lame, lawful, lax, light, light-boned, light-handed, limp, loggerheaded, low, low-powered, lowly, lubberly, lumpen, lumpish, manlike, menial, namby-pamby, nerveless, nightly, nitwitted, noticeable, obtuse, official, orderly, out of practice, overdelicate, pale, pallid, palpable, pastel, perceivable, perceptible, powerless, prescribed, puny, recognizable, regular, regularised, regularized, rhythmic, rhythmical, rickety, rough, routine, rule-governed, rusty, sapless, seeable, semiskilled, senseless, sensible, set, shoddy, sick, slack, slight, slow, soft, soft-witted, spineless, standard, stock, stupid, subtle, symmetric, symmetrical, systematic, tender, tenuous, thick, thick-skulled, thickheaded, thin, thinned, thrown, timed, unaccented, undependable, uneffective, unemphatic, uniform, unintelligent, unreliable, unskilled, unskillful, unstressed, unthinking, untoughened, visible, vulnerable, wan, washy, watery, weak, weakened, weakly, well-ordered, white, wishy-washy, witless, wooden-headed, yokel-like

weak is a ADJ.