class spouse

A friend, usually of the opposite sex, that you get to know and chat with in a class because your other, better friends aren't in that class. Sometimes leads to hurt feelings down the line when one party mistakes it for romantic attraction. Similar to a "work spouse" at a job.

I didn't know Derek before this semester, but we sit next to each other in Trigonometry and are always trading jokes, so now he's my class spouse.