Definitions for "Half nelson"
A hold in which one arm is thrust under the corresponding arm of the opponent, generally behind, and the hand placed upon the back of his neck. In the full nelson both hands are so placed.
a wrestling hold in which the holder puts an arm under the opponent's arm and exerts press on the back of the neck
a wrestling hold in which the holder wraps his or her forearm under his or her opponent's underarm and rests his or her hand behind the nape of the held person's (his or her) neck