Trefoil

      /\ /\
     /  \  \
    /  / \  \
   /_ /______\
     /     \
    /_______\

There is also a plane algebraic curve curve that looks like a trefoil. It has equation
x⁴ +x²y² + y⁴ = x(x² -y²).

A three-leaved clover representing the three parts of the Girl Scout Promise. Also a very yummy shortbread Girl Scout Cookie.

Tre"foil (?), n. [L. tres three + E. foil leaf; cf. F. frefle, 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.

2. Arch.

An ornamental foliation consisting of three divisions, or foils.

3. Her.

A charge representing the clover leaf.

© Webster 1913.