How do you creampie?

I would say it is a slang for vagina that has reached orgasm.

Ejaculation inside the partner's vagina or anus without the use of a condom.

Ejaculate inside a womens vagina or anus

A creampie is the act of a male ejaculating inside a woman's vagina or anus, or in a man's anus is a creampie too.