kopoo
1: a violent way of striking someone with your forehead to inflict pain so that they get to understand who's the real mbinga ("boss").
2: a technique that's unique to soccer (or association football) where players use their heads to maneuver the ball in mid-air toward whatever direction they want it to go.
Pronunciation
Kopoo is pronounced as /kôl · pōl/ but definitely not /kôl · po͞ol/ which happens to be a common mistake.