trefoil definition by Webster's New World
- any of a number of plants with leaves divided into three leaflets, as the clover, tick trefoil, and certain species of lotus
- a flower or leaf with three lobes
- any ornamental figure resembling a threefold leaf
Origin: Middle English treyfoyle ; from Anglo-French trifoil ; from Classical Latin trifolium, three-leaved plant ; from tri-, tri- plush folium, a leaf: see foil
trefoil definition by American Heritage Dictionary
- Any of various plants of the genera Trifolium, Lotus, and related genera of the pea family, having compound trifoliate leaves.
- An ornament, symbol, or architectural form having the appearance of a trifoliate leaf.
Origin: Middle English, from Anglo-Norman trifoil, from Latin trifolium : tri-, tri- + folium, leaf; see bhel-3 in Indo-European roots.