'Filth knuckle' when you're knuckle deep in pussy and the lass hasn't the best personal hygiene... when your finger(s) come up for breath you have a suspicious brown stain on the back of your knuckle(s).
I've never had such bad filth knuckle as last night... it was like I'd been eating dark chocolate with the back of my hand.
by Huw Jorgan February 16, 2016