Rats are mouse-like rodents with long tails, pointed noses, and whiskers. Rats are often associated with filth and disease. So, if someone calls you a rat, it's not like being called a fox. It's an insult.

Many people keep rats as pets, and scientists often study rats because their psychological behavior is actually very similar to that of humans. Rats are intelligent and adaptable, but wild rats also carry disease and sometimes bite humans. These negative traits have led to the informal meaning of rat, "hateful person," "liar," or "double-crosser." You can also use rat as a verb to mean "betray or snitch on."

Definitions of rat
  1. noun
    any of various long-tailed rodents similar to but larger than a mouse
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    pocket rat
    any of various rodents with cheek pouches
    Norway rat, Rattus norvegicus, brown rat
    common domestic rat; serious pest worldwide
    Rattus rattus, black rat, roof rat
    common household pest originally from Asia that has spread worldwide
    bandicoot rat, mole rat
    burrowing scaly-tailed rat of India and Ceylon
    jerboa rat
    large Australian rat with hind legs adapted for leaping
    Oryzomys palustris, rice rat
    hardy agile rat of grassy marshes of Mexico and the southeastern United States
    wharf rat
    brown rat that infests wharves
    sewer rat
    brown rat commonly found in sewers
    kangaroo mouse
    leaping rodent of Australian desert areas
    pocket mouse
    any of various small nocturnal burrowing desert rodents with cheek pouches and long hind legs and tail
    Dipodomys phillipsii, desert rat, kangaroo rat
    any of various leaping rodents of desert regions of North America and Mexico; largest members of the family Heteromyidae
    dwarf pocket rat, kangaroo mouse
    small silky-haired pouched rodent; similar to but smaller than kangaroo rats
    gopher, pocket gopher, pouched rat
    burrowing rodent of the family Geomyidae having large external cheek pouches; of Central America and southwestern North America
    type of:
    gnawer, rodent
    relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing
  2. verb
    catch rats, especially with dogs
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    type of:
    capture, catch
    capture as if by hunting, snaring, or trapping
  3. noun
    a person who is deemed to be despicable or contemptible
    “kill the rat
    synonyms: bum, crumb, dirty dog, git, lowlife, puke, rotter, skunk, so-and-so, stinker, stinkpot
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    type of:
    disagreeable person, unpleasant person
    a person who is not pleasant or agreeable
  4. noun
    one who reveals confidential information in return for money
    synonyms: betrayer, blabber, informer, squealer
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    canary, fink, sneak, sneaker, snitch, snitcher, stool pigeon, stoolie, stoolpigeon
    someone acting as an informer or decoy for the police
    copper's nark, nark
    an informer or spy working for the police
    grass, supergrass
    a police informer who implicates many people
    type of:
    informant, source
    a person who supplies information
  5. verb
    give away information about somebody
    synonyms: betray, denounce, give away, grass, shop, snitch, stag, tell on
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    sell out
    give information that compromises others
    type of:
    impart knowledge of some fact, state or affairs, or event to
  6. verb
    desert one's party or group of friends, for example, for one's personal advantage
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    type of:
    defect, desert
    desert (a cause, a country or an army), often in order to join the opposing cause, country, or army
  7. noun
    a pad (usually made of hair) worn as part of a woman's coiffure
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    type of:
    a flat mass of soft material used for protection, stuffing, or comfort
  8. verb
    give (hair) the appearance of being fuller by using a rat
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    type of:
    fill out, pad
    line or stuff with soft material
  9. noun
    someone who works (or provides workers) during a strike
    synonyms: blackleg, scab, strikebreaker
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    type of:
    a person who works at a specific occupation
  10. verb
    employ scabs or strike breakers in
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    type of:
    employ, engage, hire
    engage or hire for work
  11. verb
    take the place of work of someone on strike
    synonyms: blackleg, fink, scab
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    type of:
    do work, work
    be employed
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