The Collaborative International Dictionary of English v.0.48:

Uterus \U"te*rus\, n. [L.]
   1. (Anat.) The organ of a female mammal in which the young
      are developed previous to birth; the womb.
      [1913 Webster]

   Note: The uterus is simply an enlargement of the oviduct, and
         in the lower mammals there is one on each side, but in
         the higher forms the two become more or less completely
         united into one. In many male mammals there is a small
         vesicle, opening into the urinogenital canal, which
         corresponds to the uterus of the female and is called
         the male uterus, or [NL.] uterus masculinus.
         [1913 Webster]

   2. (Zool.) A receptacle, or pouch, connected with the
      oviducts of many invertebrates in which the eggs are
      retained until they hatch or until the embryos develop
      more or less. See Illust. of Hermaphrodite in Append.
      [1913 Webster]

WordNet (r) 3.0 (2006):

uterus
    n 1: a hollow muscular organ in the pelvic cavity of females;
         contains the developing fetus [syn: uterus, womb]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "uterus":
   bag, ballocks, balls, basket, beard, breasts, cervix, clitoris,
   cod, cods, cullions, family jewels, female organs, genitalia,
   genitals, gonads, labia, labia majora, labia minora, lingam, lips,
   male organs, matrix, meat, nuts, nymphae, ovary, penis, phallus,
   private parts, privates, privy parts, pubic hair, pudenda,
   reproductive organs, rocks, scrotum, secondary sex characteristic,
   sex organs, spermary, testes, testicles, vagina, venter, vulva,
   womb, yoni