Synonyms and related words :
amateurish, brainless, foolish, headless, ignorant, incapable, incapable of, incompetent, ineffective, inefficient, inept, inferior, insensate, irrational, lackbrained, lean-minded, lean-witted, mindless, not bright, of little brain, pea-brained, pin-brained, reasonless, semiskilled, senseless, slackminded, slackwitted, unable, unable to, unaccomplished, unbusinesslike, uncoached, unendowed, unfinished, unfit, unfitted, ungifted, uninitiated, unintellectual, unintelligent, unpolished, unprepared, unprimed, unprofessional, unqualified, unreasoning, unschooled, unskilled, untaught, unthinking, untrained, untutored, unwise, witless