When you take a shit in someone's luggage. You then close the luggage and put it away to be found later.
"Man, that Mike is a real douche. Wait until he gets packing and finds a shallow grave."
A sexual position in which the female partner appears to be dead or lying on the back facing upward. The male partner therefore fucks her while he is on his knees. When having sex the male partner looks as though he is fucking a body that is in a "shallow grave". This position looks as though it is derived from necrophilia.
"I fucked her in a shallow grave."
"I fucked her while she lied down. I was on my knees."