the hard part of the foot of some animals, for example horses （马等动物的）蹄 
The horse tossed its head and stamped its hooves nervously. 那匹马摇晃着头，紧张地跺着蹄子。
Oxford Collocations DictionaryHoof is used before these nouns:- beat
- horse
Word OriginOld English hōf, of Germanic origin; related to Dutch hoef and German Huf.
Idioms
on the hoof
meat that is sold, transported, etc. on the hoof is sold, etc. while the cow, sheep, etc. is still alive （牲畜等）活着的，待宰的 - (British English, informal)
if you do something on the hoof, you do it quickly and without giving it your full attention because you are doing something else at the same time 草草地；顺便 I often have lunch on the hoof between two appointments. 我经常在两次约会之间匆忙吃午饭。 the consequences of making government policy on the hoof 匆忙制定政府政策的后果