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 Ariesn. at pointn.1 Phrases P.5a).
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. Astronomyi. iii. 31
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
2000
The On the Line partnership..is an educational programme to help children learn about other people living along the zero meridian.
zero meridian typically occurs about 0.01 times per million words in modern written English.
zero meridian is in frequency band 3, which contains words occurring between 0.01 and 0.1 times per million words in modern written English. More about OED's frequency bands
Frequency data is computed programmatically, and should be regarded as an estimate.
Frequency of zero meridian, n., 1860–2010
* Occurrences per million words in written English
Historical frequency series are derived from Google Books Ngrams (version 2), a data set based on the Google Books corpus of several million books printed in English between 1500 and 2010.
The overall frequency for a given word is calculated by summing frequencies for the main form of the word, any plural or inflected forms, and any major spelling variations.
For sets of homographs (distinct entries that share the same word-form, e.g. mole, n.¹, mole, n.², mole, n.³, etc.), we have estimated the frequency of each homograph entry as a fraction of the total Ngrams frequency for the word-form. This may result in inaccuracies.
Smoothing has been applied to series for lower-frequency words, using a moving-average algorithm. This reduces short-term fluctuations, which may be produced by variability in the content of the Google Books corpus.
Decade
Frequency per million words
1860
0.0044
1870
0.0059
1880
0.0062
1890
0.0065
1900
0.0075
1910
0.01
1920
0.011
1930
0.011
1940
0.011
1950
0.011
1960
0.011
1970
0.011
1980
0.01
1990
0.0097
2000
0.009
2010
0.0088
Originally published as part of the entry for zero, n. & adj.