trefoil Meaning, Definition & Usage

  1. noun any of several Old World herbs of the genus Medicago having small flowers and trifoliate compound leaves
    medic; medick.
  2. noun a plant of the genus Trifolium
    clover.
  3. noun an architectural ornament in the form of three arcs arranged in a circle

WordNet

Tre"foil noun
Etymology
L. tres three + E. foil leaf; cf. F. frèfle, It. trifoglio, L. trifolium. See Tri-, Foil leaf, and cf. Trifoly.
Definitions
  1. (Bot.) Any plant of the genus Trifolium, which includes the white clover, red clover, etc.; -- less properly, applied also to the nonesuch, or black medic. See Clover, and Medic.
  2. (Arch.) An ornamental foliation consisting of three divisions, or foils.
  3. (Her.) A charge representing the clover leaf.

Webster 1913