Noun, pl. fetuses
1. A developing mammal or other viviparous vertebrate after the embryonic stage and before birth.
In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization. (wikipedia.org)
2. A developing unborn offspring of an animal that gives birth to its young (as opposed to laying eggs). (biology-online.org)
3. An unborn or unhatched vertebrate showing signs of the mature animal. (wiktionary.org)
4. A human embryo after the 8th week of gestation. (wiktionary.org)
5. An unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal. (wordnetweb.princeton.edu)
Word origin: From Latin fetus (often, incorrectly, foetus) “the bearing, bringing forth, or hatching of young,” from Latin base *fe- “to generate, bear,” also “to suck, suckle”.