the hard part of the foot of some animals, for example horses （馬等動物的）蹄 
The horse tossed its head and stamped its hooves nervously. 那匹馬搖晃着頭，緊張地跺着蹄子。
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；順便 I often have lunch on the hoof between two appointments. 我經常在兩次約會之間匆忙吃午飯。 the consequences of making government policy on the hoof 匆忙制定政府政策的後果