To have more fun than someone else.
You: "I stayed home last night and cleaned my apt. with my roomie and then we watched Wizard of Oz on Netflix and crashed. What'd you do?"
Your friend: "I went to a bumpin all-night toga party with that fox Sarah, and we did the grind, and now we're an item. Good times had by all.
You: "Well, guess you outfunned me!"