A dom, usually one which, as the name suggests, is in the closet. They are usually inexperienced with sex.
This is unlike a under-dom, as the closet dom does not want to believe they are a dom, or they want to be a sub, but in reality they cannot help themselves from their inner dom. Not to say they are particularly dominant in secret, but that they are in the end the dominant one.
Vel: "I bet Karl is a closet dom; he wants to be a sub, but he's really a dom.