zero-linehttp://www.oed.com/dictionary/zero-line_n%3Ftab%3Dmeaning_and_usezero-line, n.
Revised 2018

zero-linenoun

  1. 1834–
    A line represented by 0 on a scale or instrument, used as the basis for taking measurements; (also) a value from which a positive or negative quantity is reckoned, a baseline. cf. zero n. A.4a, zero n. A.4b.
    1. 1834
      Its zero line should be a continuation of the inner edge of such bar, when viewed through the telescope.
      Mem. Royal Astron. Society vol. 7 14
    2. 1915
      The horizontal or zero line, which crosses the hinder and lower angles of the right and left parietal bones.
      A. Keith, Antiquity of Man xxi. 341
    3. 2010
      When the bars cross below the zero line from above and continue falling below it, this is generally a strong indication of bearish price momentum.
      J. Chen, Essent. Technical Anal. Financial Markets xiv. 253

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

zero, n. & adj. was revised in June 2018.