n.[C]

1. 鼠
   Rats carry very nasty diseases.

   老鼠传播讨厌的疾病。

2. 【口】卑鄙小人；叛徒；告密者
3. 【美】【口】女用发垫

vi.

1. 捕鼠
   The cat went ratting.

   猫去捉老鼠了。

2. 背叛；密告[（+on）]
   They said they'd help but they've ratted on their friends.

   他们说他们会帮忙的，但他们却背叛了朋友。

n.

1. a rodent resembling a large, long-tailed mouse, typically considered a serious pest. [Rattus norvegicus (brown rat), R. rattus (black or ship rat), and many other species.]
2. informal a despicable person.
   ▸an informer.
3. N. Amer. informal a person who is associated with or frequents a specified place:
   a mall rat.

exclam.

v.

1. hunt or kill rats.
2. informal desert one's party, side, or cause.
   ▸ (rat on) break (an agreement or promise).
3. (rat on or N. Amer. also rat someone out) informal inform on (someone).