trefoil

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various plants of the genera Trifolium, Lotus, and related genera of the pea family, having compound trifoliate leaves.
2. n. An ornament, symbol, or architectural form having the appearance of a trifoliate leaf.

Century Dictionary and Cyclopedia

1. n. In anatomy, the triangular area which forms the front part of a molar tooth; the protocone, paracone, and metacone lying at the angles. Same as trigon, 6.
2. n. A plant of the genus Trifolium; clover. The name is given to various other plants with trifoliolate leaves, in England somewhat specifically to the black medic, Medicago lupulina, grown for pasture. See clover, Stylosanthes, and specific names below.
3. n. The third leaf put forth by a young plant.
4. n. An ornamental feathering or foliation used in medieval Pointed architecture in the heads of window-lights, tracery, panelings, etc., in which the spaces between the cusps represent a three-lobed figure.
5. n. In heraldry, a bearing supposed to represent a clover-leaf. It consists usually of three rounded and slightly pointed leaves set in a formal way at the three upper extremities of a small cross, the lower extremity of which terminates in different ways. Also trefle.
6. n. A bombycid moth, Lasiocampa trifolii, whose larva feeds on grass and clover in Europe. Also called grass-egger and clover-egger.
7. Characterized by the presence or prominence of a trefoil or trefoils; consisting of trefoils; thrice foliated.

Wiktionary

1. n. botany Any of several plants of the pea family, having compound, trifoliate leaves; especially one of the genus Trifolium.
2. n. A symbol having the shape of such leaves, especially when used as an architectural ornament.

GNU Webster's 1913

1. n. (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. n. (Arch.) An ornamental foliation consisting of three divisions, or foils.
3. n. (Her.) A charge representing the clover leaf.

WordNet 3.0

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