Going on a double date with a friend and their boyfriend/girlfriend , and you get paired with someone who is the friend of your friends girlfriend/boyfriend.
However, you usually haven't met them before or you are not attracted to them.
You do this so the friend of the gf/bf doesnt feel left out in anyway or because your friend needs support on their first date with a certain girl or boy and won't go alone.
Person A: Yo why was you at the movies with that Ashley girl ?
Person: Man, I don't even know her, I was on a Favour Date !