cat-o'-nine-tails \ˌkad.əˈnīnˌtālz, ˌkatənˈī-, ˌkatəˈnī-\noun (pluralcat-o'-nine-tails) Etymology: so called from a comparison of its blows to the scratches of a cat 1.: a whip made of usually nine knotted lines or cords fastened to a handle and used for flogging 2.: cattail