cat-o'-nine-tails
noun [ S ] uk/ˌkæt.əˈnaɪn.teɪlz/ us/ˌkæt̬.əˈnaɪn.teɪlz/ (informal cat)
（旧时用于体罚的）九尾鞭
a whip (= a long, thin device for hitting) made from rope that has nine ends, that was used especially in the past for hitting people to punish them