/ ˈtrefɔɪl; NAmE ; ˈtri:fɔɪl/ noun
1.
( technical ) a plant whose leaves are divided into three similar parts, for example clover
2.
a decoration or a design shaped like a trefoil leaf
••
WORD ORIGIN
Middle English : from Anglo-Norman French trifoil , from Latin trifolium , from tri- three + folium leaf.