n. An excessive accumulation; a superfluous addition.
n. The formation of a fetus while another fetus is already present in the uterus.
the GNU version of the Collaborative International Dictionary of English
n. 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.
The Century Dictionary and Cyclopedia
n. A second conception some time after a prior one, by which two fetuses of different age exist together in the same female: often used figuratively.
n. The fetus produced by superfetation; hence, any excrescent growth.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. fertilization of a second ovum after a pregnancy has begun; results in two fetuses of different ages in the uterus at the same time
Word Usage
"There have been only 10 recorded cases of the phenomenon, dubbed superfetation."