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Phrase(s): *armed and dangerous
Cliché [of someone who is suspected of a crime] having a gun or other lethal weapon and not being reluctant to use it. (This is part of a warning to police officers who might try to capture an armed suspect. *Typically: be ~; be regarded as ~; be presumed to be ~.) • The murderer is at large, presumed to be armed and dangerous. • The suspect has killed once and is armed and dangerous.
McGrawhill's American Idioms And Phrasal Verbs