As an orgasm is good, an antiorgasm is bad. Usually refering to a body experiance, or something that rapidly changes your mood towards the negative.
Little Johny was kicked in the crotch, he had an antiorgasm. Little Jimmy excitedly ran up the stairs, slipping and banging his head, it was antiorgasmic. Old Johny was having his way with a kind lady, when she snipped off his hose, instead of orgasming, he had an antiorgasm.