The Collaborative International Dictionary of English v.0.48:

Apish \Ap"ish\, a.
   Having the qualities of an ape; prone to imitate in a servile
   manner. Hence: Apelike; fantastically silly; foppish;
   affected; trifling.
   [1913 Webster]

         The apish gallantry of a fantastic boy.  --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

apish
    adj 1: being or given to servile imitation [syn: apish,
           apelike]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "apish":
   asinine, batty, befooled, beguiled, besotted, brainless,
   buffoonish, cockeyed, crazy, credulous, daffy, daft, dazed,
   delineatory, depictive, dizzy, doting, dumb, echoic, embodying,
   emulative, fatuitous, fatuous, figurative, flaky, fond, fool,
   foolheaded, foolish, fuddled, futile, gaga, goofy, graphic, gulled,
   ideographic, idiotic, illustrational, illustrative, imbecile,
   imitative, inane, incarnating, inept, infatuated, insane, kooky,
   limning, loony, mad, maudlin, mimetic, mimic, mimish, moronic,
   nutty, onomatopoeic, onomatopoetic, personifying, pictographic,
   pictorial, portraying, representational, representative,
   representing, sappy, screwy, senseless, sentimental, silly,
   simulative, stupid, symbolizing, thoughtless, typifying, vivid,
   wacky, wet, witless