A souvenir that a bro acquires after getting laid. Usually, but not limited to, a piece of clothing, such as a bra or panties.
Bro #1: "When I woke up this morning I found that Cindy wasn't in my bed still but she left me a nice bromento."
Bro #2: "Nice bro!"
*The two bros proceed to do a very chill handshake."