i depends. If you are a doctor, the word for it is incision.
orifice
Flesh, figure, and anatomical frame can substitute for human body. If you are talking about a dead human body, you can use the word corpse.
Another word of integumentary is covering or hiding.
hole
The word coccygeal is another name for the tailbone in a human's body. It is the last of the vertebral columns in the back.
ace
hole
hole
ditch
Hole, dental carie.
swallow hole
That is just a slang word. Butt is a common word that just means "end," like the end of a cigarette or a rifle. So the back end of the body, and the word hole makes it more specific that you mean the opening. Thus the opening in the back of the human body.