A friend or acquaintance who has also had sexual intercourse with the same parter that you currently have, or have had sexual intercourse with.
A: Hey, you're fucking Samantha?
B: Yes.
A: We used to be friends with benefits back in college! This makes us pump brothers!
B: Yes.
A: We used to be friends with benefits back in college! This makes us pump brothers!
by Butts@Butts.com November 2, 2012
Get the pump brothermug.