knuckled down
to physically beat someone down with your fists
"...there's a good chance ya ass is either gon' get shot, stabbed, or knuckled down, one out of the three." - Prodigy of Mobb Deep (The Infamous Prelude)
Knuckle Down
To have a firm grip on ones cock and sucking them off with your knuckle's bulging out of your hand to show your hard work.
Heather popped a vein in her hand after she knuckled down hard on Mikie!!!
knuckles down
Sly way of saying jerking off.
I was knuckles down crushin my beef.
beef knuckle beat down
to have sex
Remember that girl from biology class? I totally gave her the ol' beef knuckle beat down.