A punch delivered in a semicircular motion or direction, as opposed to straight in front of the person delivering it. The boxer was caught with a vicious roundhouse punch that KO'd him on the spot.You're better off throwing quick, controlled jabs than swinging those wild roundhouses punches.
roundhouse punch
n. a punch to the head made by swinging the arm in an arc rather than by a jabbing punch. He let him have a roundhouse punch that would have cracked a two-by-four.