1) when you like/love two people at once, not necessarily resulting in cheating on one of them with the other.
2) when someone dates another person, breaks up with them, and dates their best friend.
Joe: Man, I'm in double trouble. I like Mary and Alissa.
Rob: Can't help you there. But can I have the one you don't pick?
Nicole: If you ask me, Marina's getting into double trouble. She went from Travis to Nick and those two are like, supertight.
Kim: Yeah, she's bound to be disappointed.