superfecundation
(n) The term applied to the exceedingly (depending where one lives) rare situation where two (possibly more) seperate eggs from a woman are fertilized by sperm from two (or more) men.
Chan never did know why his fraternal twin brother was black until he heard of the term superfecundation. He never looked at his mother the same way again.
heteropaternal superfecundation
An Ultra-rare situation created by gangbanging a girl, unprotected, while she's utilizing fertility drugs, in extremely short durations.
I'm sorry, but you are now pregnant with 15 fraternal twins, from your last gangbang. The scientific definition for this is heteropaternal superfecundation.