A "cousband" is one who is of relation to you (cousin) BUT wants to marry you (husband) and have your babies.
They do not care that this is incestuous, and you may be the only one in the family that they do not want to kill.
Never drive alone with this person, and avoid at all cost, especially if they attend the same university as you.
You: "Ya, sure."
*One hour later, in car*
Cousband: "If we weren't related, I could see myself being with you."
Susan: "Martha! You look great! Who's this lucky fellow?"
Martha: *gesturing to Jerry* "This is my cousband! We met at the reunion a few years ago."
Susan: "Awwww, do you have any kids?"
Martha: "Oh yes! You should see them; a bunch of little mutants!" *smile*