(Anat.) The organ of a female mammal in which the young are developed previous to birth; the womb. 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 uterus masculinus.