The Rectus Abdominis is a long flat muscle that runs down the front of the abdomen. It is more commonly known as a six-pack on the body and can be seen in muscly/athletic people.
"WOW!!! your Rectus Abdominis is huge man, how do you get it like that?"
"You mean my six-pack?, just weight lifting"
During the ejaculatory phase of a male/female sexual encounter, if the male participant withdraws his penis and ejects semen onto the famale participant's abdomen, this is referred to as an "abdominal snowman."
I didn't want to get that fuckin' bitchpregnant, so I was raw doggin' her and gave her an abdominal snowman instead of blowing my load up her cooch.