\Su`per*fe*ta"tion\, n. [Cf. F. superf['e]tation.]
(Physiol.)
The formation of a fetus at the result of an impregnation
occurring after another impregnation but before the birth of
the offspring produced by it. This is possible only when
there is a double uterus, or where menstruation persists up
to the time of the second impregnation.
      In then became a superfetation upon, and not an
      ingredient in, the national character.   --Coleridge.