Antimeridian

noun

noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    The reference line at 180° longitude, on the opposite side of earth to the prime meridian.

    "On the opposite side of the Earth from Greenwich is the antimeridian, a line of longitude that is 180° both east and west of the prime meridian. It cuts through parts of eastern Russia, the Fiji Islands and the middle of the Pacific Ocean."

  2. 2
    A meridian of longitude opposite to any given meridian used as a point of reference.

    "123° west is the antimeridian of the 57° east meridian."

Synonyms

All synonyms
greenwich antimeridian

Example

More examples

"On the opposite side of the Earth from Greenwich is the antimeridian, a line of longitude that is 180° both east and west of the prime meridian. It cuts through parts of eastern Russia, the Fiji Islands and the middle of the Pacific Ocean."

Etymology

From anti- + meridian.

Related phrases

prime meridian

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.