Green’s Dictionary of Slang

(orig. US teen) a snack.

1982		W. Safire What’s the Good Word? 304: ‘Dinner’ is a ‘major munch’.
2003		Spud ‘Marijuana’ page on Spud’s Page 🌐 That’s about it for now, I don’t know about you but I fancy a munch!
2015		L. McInerney Glorious Heresies 263: [M]e and Karine were out for a munch.
2020		G. Armstrong Young Team 92: [T]hinkin aboot ma lunchtime munch.