zero-meridianhttp://www.oed.com/dictionary/zero-meridian_n%3Ftab%3Dmeaning_and_usezero meridian, n.
First published 2017

zero meridiannoun

  1. 1849–
    a. A meridian representing the zero of longitude; esp. the prime meridian through Greenwich; b. (Astronomy) the meridian through the first point of Aries, from which right ascension is measured (cf. first point of Aries n. at point n.1 Phrases P.5a).
    1. 1849
      Astronomers have agreed to take that meridian for the zero meridian, which passes through the sun's center the instant the sun comes to the celestial equator, in the spring.
      H. N. Robinson, Treat. Astronomy i. iii. 31
    2. 1939
      The reckoning always starting from the equator for latitude, and for longitude from zero meridian which may differ in different countries.
      E. D. Laborde, translation of E. de Martonne, Shorter Physical Geography (revised edition) 5
    3. 2000
      The On the Line partnership..is an educational programme to help children learn about other people living along the zero meridian.
      CEEmail Summer 12/3

Originally published as part of the entry for zero, n. & adj.

zero meridian, n. was first published in 2017.