eat (one's) lunch(redirected from eat their lunch)
eat (one's) lunch
slang To defeat one. I've been practicing really hard because I refuse to let my nemesis eat my lunch again.
eat someone's lunch
Sl. to best someone; to defeat, outwit, or win against someone. (Like a school bully taking away children's lunches and eating them.) The upstart ABC Computer Company is eating IBM's lunch.