1
- a fully grown female animal of a domesticated breed of ox, used as a source of milk or beef奶牛, 乳牛; 肉用母牛：
a dairy cow.
一头乳牛。见CATTLE.
1.1
- (loosely) a domestic bovine animal, regardless of sex or age（泛指）牛。
1.2
- (in farming) a female domestic bovine animal which has borne more than one calf（畜牧业中已生了一头以上小牛的）母牛。比较 HEIFER.
1.3
- the female of certain other large animals, for example elephant, rhinoceros, whale, seal, or reindeer（大型）母兽（如大象、犀牛、鲸、海豹、驯鹿等）。
2
- informal, derogatory a woman〈非正式, 贬〉婆娘, 女人。
2.1
- Austral./NZ an unpleasant person, thing, or situation〈澳/新西兰〉令人不快的人（或事物、处境）。
短语
have a cow
- N. Amer. informal become angry, excited, or agitated〈北美, 非正式〉发怒; 变得激动（或焦虑不安）起来：
don't have a cow - it's no big deal.
别着急——没什么大不了。
till the cows come home
- informal for an indefinitely long time〈非正式〉长时间地; 没完没了地：
those two could talk till the cows came home.
那两个人可能会没完没了地聊下去。
词源
Old English cū, of Germanic origin; related to Dutch koe and German Kuh, from an Indo-European root shared by Latin bos and Greek bous.