noogie

[noo g-ee]

noun Slang.

a light blow or jab, usually to a person's head, back, or upper arm and accompanied by a twisting motion, with the extended knuckle of the curled-up second or third finger: done as a gesture of affection or painfully as a prank.

Also nug·gie, nug·ie.

Origin of noogie

1975–80; apparently expressive alteration of knuckle; see -y²