Small, whitish, particles or crumb-like residue typically found on bed sheets the day after a heavy session of pussy-banging. The volume of fuck crunchies directly varies with: 1) the amount of "wetness" that had been experienced by the woman's pussy, 2) the amount of coming by both parties.
My buddy Ethan sat down on my bed, but was entirely disgusted when he realized that he'd sat in a minefield of fuck crunchies from me & Liz the night before.
When my girlfriend came home and took her pants and panties off and laid on the bed. I later went up and saw dried up cunt crunchies on her pubic hairs.
The crumbs of various foodstuffs found when the keyboard is turned upside-down, and shaken or banged on the desk. These usually consists of, but are not limited to: Cheez-its, Doritos, sandwich/bread crumbs, dust and hair.