2. Literally: Crusty build-up around the genitals due to a nasty lack of personal hygiene. Not to be confused with crotch crickets.
Jake: "What's his problem?"
Bobby: "Don't mind him, he's just being a crotch crumb..."
Jane: "Would you rather dive into a pool of snot, or sleep with 'funky Jake'?"
Jenny: "Eww, gross! I hear he's got a major grody case of crotch crumb."
'There's none left in the bag but you can have my crotch crumbs'.