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noun frontier pronunciation in American English /frʌnˈtɪr/ 
Word Forms
  1. 1
    [countable] a border between two countries, especially one with official points where people or vehicles cross
    frontier between:

    the frontier between Israel and Lebanon

    frontier with:

    Italy's frontier with Switzerland

    on/at the frontier:

    troops massing at the frontier

    1. c.
      [only before noun] on or relating to a frontier

      frontier controls

      a frontier town

      frontier post (=official place for crossing):

      Armed police manned the frontier post.

  2. 2
    [countable] [usually plural] the most advanced or recent ideas about something
    the frontiers of knowledge/science/technology:

    Their work was on the frontiers of science.

    extend/push back the frontiers (=discover more):

    We are dedicated to experimentation, to pushing back the frontiers.


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