1)The act of engaging in vaginal sexual intercourse with an already impregnated woman.
2)Getting your penis all up in that fetus.
3)Poking a baby in the face (with your penis, of course).
John: Yo, Alex did you plow Tiffany last night?
Alex: Hell yah John you know it!
John: Dude, she's four months pregnant with Tim's baby. You got that fetus penis!!!
Alex: Shutup man.
John: Alright, alright............. Fetus penis.
Fetus penis: That shit your daddy probably resorted to.
An poor poor man with a very tiny penis. Resembles the penis of an aborted fetus it is so small
Dude did you see that guys dong? He had a damn fetus penis.