any of several long-tailed rodents of the family Muridae, of the genus Rattus and related genera, distinguished from the mouse by being larger.

any of various similar or related animals.

Slang . a scoundrel.

Slang .

a person who abandons or betrays his or her party or associates, esp. in a time of trouble.

an informer.

a scab laborer.

Slang . a person who frequents a specified place

a mall rat; gym rats.

a pad with tapered ends formerly used in women's hair styles to give the appearance of greater thickness.

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

Slang .

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.

to hunt or catch rats.

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

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.

noun

backstabber , betrayer , blabbermouth * , canary * , deep throat , double-crosser , fink , informant , sneak , snitch , source , squealer , stoolie , stool pigeon * , tattler , tattletale , turncoat , whistle-blower , judas , traitor , apostate , deserter , recreant , renegade , runagate , tergiversator , defect , inform , informer , pest , rodent , scab , snot , stool pigeon , vermin

verb

apostatize , desert , renegade , tergiversate , turn , double-cross , talk , tattle , tip