a/(one's) plus-one
A guest whom one is permitted to bring to an event. I don't want to go to the wedding alone, so I'm bringing Maggie as my plus-one. She loves to dance, so I know we'll have a good time. Maybe he's not her boyfriend. He could just be a plus one—a friend or something. Wow, who's Pete's plus-one? She's gorgeous!
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.