a whip used as an instrument of punishment consisting of nine pieces of knotted line or cord fastened to a handle; -- formerly used to flog offenders on the bare back; -- called also the cat. It was used in the British Navy to maintain discipline on board sailing ships.

When a soldier was ordered to be punished, the most common punishment was the administration of lashes by the drummers of the regiment. The drummer would whip the offender with a Cat o' Nine Tails, a leather whip with nine knotted cords or strands.

A short nine-tailed whip kept by the bosun's mate to flog sailors (and soldiers in the Army).