How about - faithful : false, faithless featured : flat (as in terrain) foreign : familiar groovy : gross helpful : hurtful intelligent : idiotic, imbecilic joyful, jovial : joyless lovely : lousy normal : nutty, non-normal open : opaque, obstructed passive : pig-headed stop : start (e.g. stop sign : start signal) timely : tardy unhappy : untroubled wide : wiry yucky : yummy zenlike : zesty More of the obvious ones :P wired : wireless windless : windy What was your list?