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REFERENCE

traitor

n.
US //ˈtɹeɪtɝ// UK //tɹˈeɪtɐ// traitor
  1. 1 betraying a country (n.)
    B2 Upper Intermediate Law

    someone who helps an enemy of their own country or gives away national secrets.

    a person who violates an allegiance to their state or sovereign by aiding an enemy or committing treason.

    Example

    The soldier was caught selling secret documents and was branded a traitor to his country.

    Example

    History remembers him as a traitor who provided the invading forces with the exact coordinates of the coastal defences.
  2. 2 betraying a person or group (n.)
    B2 Upper Intermediate Informal

    someone who is not loyal to their friends or a group they belong to.

    one who betrays a personal confidence, a shared cause, or a social group.

    Example

    My friends called me a traitor because I started supporting the rival football team.

    Example

    In the cutthroat world of corporate politics, he was viewed as a traitor for leaking the merger details to the press.
    • backstabber
    • double crosser
Origin

From Middle English traitor, traitour, traytour, from Old French traïtor (French traître), from Latin trāditor. Displaced native Middle English swike from Old English swica (“traitor”), and Middle English proditour and traditour borrowed directly from Latin. The general Old English word denoting "traitor" was lǣwa or lǣwend. Doublet of traditor.

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