The Collaborative International Dictionary of English v.0.48:

Tush \Tush\ (t[u^]sh), interj.
   An exclamation indicating check, rebuke, or contempt; as,
   tush, tush! do not speak of it.
   [1913 Webster]

         Tush, say they, how should God perceive it? --Bk. of
                                                  Com. Prayer
                                                  (Ps. lxxiii.
                                                  11).
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tush \Tush\, n. [OE. tusch, AS. tusc; akin to OFries. tusk,
   tusch, and probably to AS. t[=o][eth] tooth. See Tooth, and
   cf. Tusk.]
   A long, pointed tooth; a tusk; -- applied especially to
   certain teeth of horses.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

tush \tush\ (t[oo^]sh), n. [Shortened form of tushie.]
   The buttocks; -- a euphemism.
   [PJC]

WordNet (r) 3.0 (2006):

tush
    n 1: the fleshy part of the human body that you sit on; "he
         deserves a good kick in the butt"; "are you going to sit on
         your fanny and do nothing?" [syn: buttocks, nates,
         arse, butt, backside, bum, buns, can,
         fundament, hindquarters, hind end, keister,
         posterior, prat, rear, rear end, rump, stern,
         seat, tail, tail end, tooshie, tush, bottom,
         behind, derriere, fanny, ass]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "tush":
   arse, ass, baby tooth, bicuspid, bucktooth, bum, can, canine,
   cheeks, crown, cuspid, cutter, deciduous tooth, dent, denticle,
   denticulation, dentil, dentition, dogtooth, eyetooth, fang, fanny,
   fore tooth, gagtooth, gang tooth, gold tooth, grinder, incisor,
   keister, milk tooth, molar, peg, permanent tooth, pivot tooth,
   prat, premolar, rusty-dusty, scrivello, snag, snaggletooth, stern,
   tail, tooth, tuchis, tushy, tusk, wisdom tooth