n.
- 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.]
- informal a despicable person.
▸an informer.
- N. Amer. informal a person who is associated with or frequents a specified place:
a mall rat.
exclam.
(
rats)
informal expressing mild annoyance.
v.
(rats, ratting, ratted)
- hunt or kill rats.
- informal desert one's party, side, or cause.
▸
(rat on)
break (an agreement or promise).
-
(rat on or N. Amer. also rat someone out)
informal inform on (someone).
Derivative
Etymology
OE ræt, prob. of Romance origin; reinforced in ME by OFr. rat.