Word
rat
US/ˈɹæt/
UK/ɹˈæt/
Definitions
01the animal
A2 · Elementary Countable noun Zoology
n. a small animal with a long tail that looks like a large mouse.
n. any of various medium-sized rodents, particularly those in the genus Rattus, characterized by a long hairless tail and a pointed snout.
日本語:ねずみ※
Español:rata
“The old warehouse was full of rats looking for food in the rubbish.”
“Urban planners must account for the resilience of rat populations when designing waste management systems for densely populated city centres.”
Synonyms
02a traitor or informant
B2 · Upper Intermediate Countable noun Informal
n. a person who is dishonest or betrays their friends or group.
n. a person who betrays a person, group, or cause; often used for an informant who gives information to the police.
日本語:いぬ※
Español:chivato
“He called his former partner a rat for telling the boss about the mistake.”
“In many underworld narratives, the character identified as the rat often faces severe consequences for violating the code of silence.”
03to inform on someone
B2 · Upper Intermediate Informal
v. to tell the police or someone in power about something bad another person did.
v. to inform on someone or betray a secret to the authorities; often used with the preposition 'on'.
“He decided to rat on his friends to avoid going to jail.”
“The witness was hesitant to rat on the gang members, fearing that the police could not provide adequate protection after the trial.”
Usage
Usually takes the preposition 'on'.
04to desert a cause
C1 · Advanced Formal
v. to leave a group or a political party when they are in trouble.
v. to desert or betray a political party, cause, or principle, especially for personal gain.
“Several members of the party chose to rat when the scandal became public.”
“The prime minister accused the defectors of ratting on the administration during its most vulnerable hour.”
Collocations
Common phrases and expressions where native English speakers use the word “rat” in context.
Verb
01. rat on his friends
“The gang members were furious when they discovered that Leo had ratted on his friends to the police.”
verb + prep + possessive + noun
02. rat out the thief
“He decided to rat out the thief in exchange for a lighter sentence.”
verb + adv + noun
03. smell a rat
“When he offered to sell me a brand new car for half price, I started to smell a rat.”
verb + noun
Adjective
04. dirty rat
“In the old gangster movie, the hero calls the traitor a dirty rat before the final showdown.”
adj + noun
05. drowned rat
“I forgot my umbrella and arrived at the office looking like a drowned rat.”
adj + noun
Noun
06. infestation of rats
“The health inspector closed the restaurant due to a severe infestation of rats in the kitchen.”
noun + of + noun
07. lab rat
“She felt like a lab rat during the medical trial, as doctors monitored her every move.”
noun + noun
08. rat race
“After twenty years in the city, he decided to quit the rat race and move to a quiet village.”
noun + noun
Real-World Examples
“To investigate whether curcumin could reduce this damage, researchers used a rat model of Type 1 diabetes.” “In a 2024 study , her team tested this possibility in groups of female rats.” Etymology
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 Hreh₃d- (“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 Hreh₃d- (“to scrape, scratch, gnaw”).
From Middle English ratten, further etymology unknown. Compare Middle Low German retten (“to tear, tear up”), Middle High German ratzen (“to scratch; rasp; tear”). Could be related to write. See also rit.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
Related words
Idioms
Domains
- Exam level
- CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.B2 FirstIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.5.5–6.5TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 4.0–4.572–94TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.785–944
- Frequency
- Common
- Level
- B2 · Upper IntermediateOxford
- Updated
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QR code
englishreference.com/q/rat
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「日本語」 data: JMdict (EDRDG), CC BY-SA 4.0
Traducciones: Kaikki.org (Wiktionary), CC BY-SA 4.0