(n) Tuft of fur between a canines toes, which often times requires grooming. In winter climates also causes animal discomfort resulting in frostbite (aka Frozen Fonzelitus).
Canine A in the dog park: "Ruff ruff.. duuddde whats that on your foot"
Canine B in the dog park: "AWW crap! I musta stepped in that Chihuahua sh_t and now its stuck in my fonzel- gotta goto the groomers again.. darnnit"...