rat

UK: /ˈræt/ US: /ræt/ ,(rat)

Inflections of 'rat' (v): (⇒ conjugate)

rats

v 3rd person singular

ratting

v pres p

ratted

v past

ratted

v past p

WordReference Random House Learner's Dictionary of American English © 2025

rat /ræt/   n., interj., v., rat•ted, rat•ting. 
n. [countable]

1. Mammals a long-tailed animal, a rodent, that resembles a mouse but is larger.
2. Slang Terms a scoundrel;
   a disloyal or untrustworthy person.
3. Slang Terms a person who abandons or betrays associates.

interj. 

4. Slang Terms rats, (used to show disgust or disappointment).

v. 

5. Slang Terms to inform on or betray one's associates:
   [~ + on] She ratted on us when the cops caught her.

rat•like, adj. 

WordReference Random House Unabridged Dictionary of American English © 2025

rat  (rat), n., interj., v., rat•ted, rat•ting. 
n. 

1. Mammals any of several long-tailed rodents of the family Muridae, of the genus Rattus and related genera, distinguished from the mouse by being larger.
2. Mammals any of various similar or related animals.
3. Slang Terms a scoundrel.
4. Slang Terms
   • a person who abandons or betrays his or her party or associates, esp. in a time of trouble.
   • an informer.
   • a scab laborer.
5. Slang Terms a person who frequents a specified place:
   mall rat; gym rat.
6. Clothing a pad with tapered ends formerly used in women's hair styles to give the appearance of greater thickness.
7. smell a rat, to suspect or surmise treachery;
   have suspicion:
   After noting several discrepancies in his client's story, the attorney began to smell a rat.

interj. 

8. Slang Terms rats, (an exclamation of disappointment, disgust, or disbelief.)

v.i. 

9. Slang Terms
   • to desert one's party or associates, esp. in a time of trouble.
   • to turn informer;
     squeal:
     He ratted on the gang, and the police arrested them.
   • to work as a scab.
10. to hunt or catch rats.

v.t. 

11. Clothing to dress (the hair) with or as if with a rat.

• bef. 1000; Middle English rat(t)e, Old English ræt; cognate with Dutch rat, German Ratz, Ratte

rat′like′, adj. 

rat, +n. 

1. Slang Terms a person who frequents a specified place:
   a mall rat; gym rats.

Collins Concise English Dictionary © HarperCollins Publishers::

rat / ræt/ noun

1. any of numerous long-tailed murine rodents, esp of the genus Rattus, that are similar to but larger than mice and are now distributed all over the world
2. a person who deserts his or her friends or associates, esp in time of trouble
3. a worker who works during a strike; blackleg; scab
4. a despicable person
5. smell a rat ⇒ to detect something suspicious

verb (rats, ratting, ratted)

1. (intransitive) usually followed by on: to divulge secret information (about); betray the trust (of)
2. to default (on); abandon
3. (intransitive) to hunt and kill rats

Etymology: Old English rætt; related to Old Saxon ratta, Old High German rato