a.
1.
Senseless, witless, dull, simple, doltish, stolid, obtuse, foolish, sluggish, insensible, brutish, insensate, muddy, muddy-brained, muddy-headed, sottish, slow of apprehension, void of understanding, fat-witted.
2.
Unentertaining, prosaic, pointless, prosy, flat, heavy, insipid, tame, vapid, bald, uninteresting, humdrum, dull, foolish, tiresome, tedious.
3.
Stupefied, drowsy, torpid, heavy, comatose, lethargic, morbidly sleepy.