• WordNet 3.6
    • n superfecundation fertilization of two or more ova released during the same menstrual cycle by sperm from separate acts of coitus (especially by different males)
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Webster's Revised Unabridged Dictionary
    • n Superfecundation (Physiol) Fertilization of two ova, at the same menstruation, by two different acts of coition.
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Century Dictionary and Cyclopedia
    • n superfecundation The fertilization of two ova at the same menstruation by two different acts of coition. This unquestionably occurs in woman.
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Chambers's Twentieth Century Dictionary
    • n Superfecundation sū-pėr-fek-un-dā′shun the impregnation of two or more ova at the same stage of development by different acts of coition.
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In literature:

His law at most merely a theory of superfecundity, 623.
"Critical and Historical Essays, Volume III (of 3)" by Thomas Babington Macaulay