Main Entry: tre·foil

Pronunciation: \ˈtrē-ˌfȯi(-ə)l, ˈtre-\

Function: noun

Etymology: Middle English, from Anglo-French, from Latin trifolium, from tri- + folium leaf — more at blade

Date: 15th century

1 a : clover 1; broadly : any of several leguminous herbs (as bird's-foot trefoil) with leaves that have or appear to have three leaflets b : a trifoliolate leaf
2 : an ornament or symbol in the form of a stylized trifoliolate leaf

[trefoil illustration]