'Trefoil' definitions:

Definition of 'trefoil'

From: WordNet
noun
Any of several Old World herbs of the genus Medicago having small flowers and trifoliate compound leaves [syn: medic, medick, trefoil]
noun
A plant of the genus Trifolium [syn: clover, trefoil]
noun
An architectural ornament in the form of three arcs arranged in a circle

Definition of 'Trefoil'

From: GCIDE
  • Trefoil \Tre"foil\, n. [L. tres three + E. foil leaf; cf. F. fr[`e]fle, It. trifoglio, L. trifolium. See Tri-, Foil leaf, and cf. Trifoly.]
  • 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. [1913 Webster]
  • 2. (Arch.) An ornamental foliation consisting of three divisions, or foils. [1913 Webster]
  • 3. (Her.) A charge representing the clover leaf. [1913 Webster]