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]