WordNet (r) 3.0 (2006):
middlebrow n 1: someone who is neither a highbrow nor a lowbrowMoby Thesaurus II by Grady Ward, 1.0:
18 Moby Thesaurus words for "middlebrow": Babbitt, boeotian, boob, dabbler, dilettante, dunce, fool, greenhorn, greeny, ignoramus, illiterate, illiterati, know-nothing, lowbrow, no scholar, puddinghead, tenderfoot, unintelligentsia