Is a phrase used in a few situations, most common is when you are seeing a girl and her
best friend likes your friend and so she wants to
double date, and the only way you are going to get with your girl is if your friend comes along to the date, but it usually turns out that her best friend is fat or sum ugly bitch that noone would fuck.
Fat bitches usually fuck things up so your friend decides to come along anyway so you can take your girl sumwhere else and bang her.