When a bro has no interest in a female due to his bro's past or present feelings for her.
Bro: Yo, you into that girl?
Bro #2: Nah dude, she's been bro-sidelined cause of Bro #3.
Bro: Shit man, I didn't know, I'll ease off then.
Bro #3: Thanks bros.
A female who is in a realionship with a fella that has one more main bitches..... however the sideline gets to ream all the benefits of a realionship..such as.. dates..public appearances..gifts...bills paid..spontaneous sex..without having to answer amy questions or go thru drama.