A drink/drinking game usually played in the barracks of combat Soldiers. The "player" is usually not made aware of the rules before hand, and is instructed by his friends to do a shot of Jager, almost immediately afterward, he is punched in the face, before he can finish the shot. The puncher usually yells Jager!.
Pvt. Snuffy arrives at his new unit, his comrades Spc Tom and Pfc Jerry want to welcome him with a Jager Punch. So Pvt. Snuffy agree's. "First you do a shot of Jager" say's Spc Tom, Pvt. Snuffy agrees and does the shot. Before he can finish, Pfc . Jerry punches him in the face, shouting 'JAGERPUNCH!' and Pvt. Snuffy spits Jager all over the place. He now must repeat until he can down ALL Jager.