z-bandhttp://www.oed.com/dictionary/z-band_n%3Ftab%3Dmeaning_and_useZ band, n.
First published 1986; not fully revised

Z bandnoun

Histology.
  1. 1950–
    1. 1950
      When a substantial degree of contraction has occurred, an appearance, often referred to as a ‘reversal of striations’, becomes apparent. This is due to the substance of the myofibril on each side of the Z band, which was formerly light, becoming dark, and the dark material of the Q band becoming light.
      A. W. Ham, Histology xix. 283/1
    2. 1964
      The segment from one Z-band to the next, along a fibril, is termed a sarcomere.
      G. H. Haggis et al., Introduction to Molecular Biology iv. 101
    3. 1970
      The major cross bands of the myofibrils are the A and I bands... In the center of the I band is a thin dark line known as the Z (Zwischenscheibe) band, or intermediate line of Krause; the Z band attaches to the sarcolemma at the periphery of the cell.
      Fallis & Ashworth, Textbook Human Histology viii. 58

Originally published as part of the entry for Z line, n.

Z line, n. was first published in 1986; not fully revised.