Synonyms and related words :
bad habit, besetting sin, blemish, bug, catch, crack, crotchet, defect, defection, deficiency, drawback, eccentricity, failing, failure, fault, faute, flaw, frailty, hang-up, hole, idiosyncrasy, imperfection, inadequacy, infirmity, kink, little problem, moral flaw, peculiarity, preoccupation, problem, quirk, rift, shortcoming, snag, something missing, taint, vice, vulnerable place, weak link, weak point, weak side, weakness