rat

Etymology 1

From Middle English ratte, rat, rotte, from Old English rætt, from Proto-West Germanic *ratt, from Proto-Germanic *rattaz, *rattō (compare West Frisian rôt, Dutch rat), of uncertain origin, possibly from Proto-Indo-European *reh₁d- (“to scrape, scratch, gnaw”). However, the rat may have been unknown in Northern Europe in antiquity, and the Proto-Germanic word may have referred to a different animal; see *rattaz for more. Attestation of this family of words begins in the 12th century. Some of the Germanic cognates show considerable consonant variation, e.g. Middle Low German ratte, radde; Middle High German rate, ratte, ratze. The irregularity may be symptomatic of a late dispersal of the word, although Kroonen accounts for it with a Proto-Germanic stem *raþō nom., *ruttaz gen., showing both ablaut and a Kluge's law alternation, with the variation arising from varying remodellings in the descendants. Kroonen states that this requires a Proto-Indo-European etymon in final *t and is incompatible with the usual derivation from Proto-Indo-European *reh₁d- (“to scrape, scratch, gnaw”).

noun

1. (zoology) A medium-sized rodent belonging to the genus Rattus.
   Similar studies of rats have employed four different intracranial resorbable, slow sustained release systems—surgical foam, a thermal gel depot, a microcapsule or biodegradable polymer beads. 2013 May-June, Charles T. Ambrose, “Alzheimer’s Disease”, in American Scientist, volume 101, number 3, page 200
2. (informal) Any of the numerous members of several rodent families (e.g. voles and mice) that resemble true rats in appearance, usually having a pointy snout, a long, bare tail, and body length greater than about 12 cm, or 5 inches.
3. (informal) A person who is known for betrayal; a scoundrel; a quisling.
   rat bastard
   What a rat, leaving us stranded here!
   Ah, so you damn rat, this is a put-up job eh? 1936, F.J. Thwaites, chapter XVIII, in The Redemption, Sydney: H. John Edwards, published 1940, page 185
4. (informal) An informant or snitch.
5. (informal) A scab: a worker who acts against trade union policies.
6. (slang) A person who routinely spends time at a particular location.
   Our teenager has become a mall rat.
   He loved hockey and was a devoted rink rat.
7. A wad of shed hair used as part of a hairstyle.
8. A roll of material used to puff out the hair, which is turned over it.
9. (UK, north-west London, slang, vulgar) Vagina.
   Get your rat out.
10. (chiefly informal) Short for muskrat.
    The price of rats began to rise and soon after the marsh froze over, spearing rats began, which was done with a one tine three-eighths inch steel rod, with a wooden handle […] 1910, L. W. Pierce, “Muskrats are fast disappearing”, in Hunter-trader-trapper, page 70
    Where natural marshes, or natural foods are found, are best places for raising muskrats. Louisiana and other southern states raise millions of rats, but they do not bring as good prices as northern raised ones. Delaware and Maryland have famed marshes. Other states are becoming noted for muskrat raising, also. 1929, E. J. Dailey, in Hardings Magazine's Question Box, printed in Fur Fish Game, page 73

verb

1. (of a dog, etc.) To hunt or kill rats.
2. (intransitive) To betray a political party, cause or principle; to betray someone, to desert a person or thing.
3. (informal, intransitive) To work as a scab, going against trade union policies.
4. (chiefly US) To backcomb (hair).
   In 1962, the higher a girl's hair was ratted the more available she was, it was simply understood. 2021, Rickie Lee Jones, Last Chance Texaco, Grove Press, published 2022, page 31
5. (intransitive, with on or out) To inform on someone; to betray someone to the police or authorities.
   He ratted on his coworker.
   He is going to rat us out!

Etymology 2

From Middle English ratten, further etymology unknown. Compare Middle High German ratzen (“to scratch; rasp; tear”). Could be related to write. See also rit.

noun

1. (regional) A scratch or a score.
2. (nautical, regional) A place in the sea with rapid currents and crags where a ship is likely to be torn apart in stormy weather.

verb

1. (regional) To scratch or score.
   He ratted a vertical line on his face with a pocket knife.
2. (regional, rare, obsolete) To tear, rip, rend.
   Ratted to shreds.
3. Damn, drat, blast; used in oaths.
   “But, rat me, sir,” cried Foster in bewilderment, “tis too generous—'pon honour it is. I can't consent to it. No, rat me, I can't.” 1904, Rafael Sabatini, chapter XXVI, in The Tavern Knight

Etymology 3

noun

1. (military, slang) A ration.
   With regards to the testing of his product, the initial blood analysis had come back confirming huge, distinctive nutritional superiority for Stewart's military ration pack. Given that the policy of the British Army is to be fully ready for war at the drop of a hat, he was sitting on the potential of supplying new rats for the entire army […] 2014, John, Buffoon, page 243