zigzag-trefoilhttp://www.oed.com/dictionary/zigzag-trefoil_n%3Ftab%3Dmeaning_and_usezigzag trefoil, n.
First published 1914; not fully revised

zigzag trefoilnoun

  1. 1796–
    Trifolium medium.
    1. 1796
      Zigzag Trefoil,..Tr. medium.
      W. Withering, Arrangement of British Plants (ed. 3) vol. III. 651
    2. 1843
      [T. medium] can be recognised by its zigzag stem, from which..it is sometimes called Zigzag Trefoil.
      Penny Cyclopaedia vol. XXV. 211/1

Originally published as part of the entry for trefoil, n.

trefoil, n. was first published in 1914; not fully revised.