rat rat /ˈræt/

noun

1. () Any of various long-tailed rodents similar to but larger than a mouse  ( rat )
   any of various long-tailed rodents similar to but larger than a mouse
    The rat scurried along the wall, searching for a way into the house
   The rat scurried along the wall, searching for a way into the house
   
   
2. A pad (usually made of hair) worn as part of a woman's coiffure  ( rat )
   a pad (usually made of hair) worn as part of a woman's coiffure
   
3. One who reveals confidential information in return for money  ( betrayer , blabber , informer , rat , squealer )
   one who reveals confidential information in return for money
   
4. [Informal] A person who is deemed to be despicable or contemptible  ( crumb [Informal, N. American] , dirty dog [Informal] , git [Informal, British] , lowlife [Informal] , rat [Informal] , rotter [Informal, British] , scum bag , so-and-so [Informal] , stinker [Informal] , stinkpot [Informal, N. American] , dirtbag [Informal, American] , ratbag [Informal, British] , scrote [British, Vulgar] , scumbag [Informal] , scuzz [Informal, N. American] , scuzzbag [Informal, N. American] , scuzzball [Informal, N. American] , scuzzbucket [Informal, N. American] , sleazebag [Informal] , sleazeball [Informal] , sleazebucket [Informal] , bum [Informal, N. American] , puke [Vulgar] , skunk [Informal] , slimebag [Informal] , slimeball [Informal] , toerag [Informal, British] )
   a person who is deemed to be despicable or contemptible
    Only a rotter would do that
   only a rotter would do that
    Kill the rat
   kill the rat
    Throw the bum out
   throw the bum out
    You cowardly little pukes!
   you cowardly little pukes!
    The British call a contemptible person a git'
   the British call a contemptible person a git'
   
5. [Informal] Someone who works (or provides workers) during a strike  ( blackleg [British] , rat [Informal] , scab , strikebreaker )
   someone who works (or provides workers) during a strike
   

verb

1. [Informal] Give away information about somebody  ( denounce , give away , grass , betray , rat [Informal] , shit [Vulgar] , shop [Informal] , snitch [Informal] , stag , tell on )
   give away information about somebody
    He told on his classmate who had cheated on the exam
   He told on his classmate who had cheated on the exam
   
2. Catch rats, especially with dogs  ( rat )
   catch rats, especially with dogs
   
3. [American] Give (hair) the appearance of being fuller by using a rat  ( rat [American] )
   give (hair) the appearance of being fuller by using a rat
   
4. [Informal] Take the place of work of someone on strike  ( blackleg [British] , fink [Informal, N. American] , rat [Informal] , scab )
   take the place of work of someone on strike
   
5. [Informal] Employ scabs or strike breakers in  ( rat [Informal] )
   employ scabs or strike breakers in
   
6. [Informal] Desert one's party or group of friends, for example, for one's personal advantage  ( rat [Informal] )
   desert one's party or group of friends, for example, for one's personal advantage