A tattoo on one's finger(s) just above or below the knuckle

plural of knuckle joint

(engineering) A joint where the forked end of a connecting rod is joined by a bolt to another piece of the machinery.

plural of knuckle bow

The curved part of a sword-guard that covers the fingers.

present participle of bare-knuckle

Boxing that is done without boxing gloves. / Ruthless competition.

present participle of bare knuckle

Alternative form of bare-knuckling

Without boxing gloves / Ruthlessly competitive