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1.
(n) A person, usually female, who is dating your best friend. Whenever you throw a party or just casually hang out, they are automatically invited to tag along because coincidentally, they are equally awesome.
Richie: "Hey buddy, are you going to watch the football games this afternoon?"

Tim: "Yeah, there are some good ones on today. I got my chips and dip, pizza and soda ready to go."

Richie: "Cool story, bro. Maybe I'll stop over later. Mind if I bring Ilsa?"

Tim: "Yeah sure. She's always welcome. Now that you two are together, she's a Bro By Association.
by LDSTex85 January 30, 2012