D defs.my
Entry 1 sense Webster, 1913

Superfetation

· Su·per·fe·ta·tion · IPA /suːpəfəˈteɪʃən/
01 n. The formation of a fetus at the result of an impregnation occurring after another impregnation but before the birth of the offspring produc…
  1. 1.
    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.(Physiol.)
    “In then became a superfetation upon, and not an ingredient in, the national character.” Coleridge.