From Longman Dictionary of Contemporary Englishtrefoiltre‧foil /ˈtriːfɔɪl, ˈtrefɔɪl/ noun [countable] technical 1 HBPa type of small plant that has leaves which divide into three parts2 CFa pattern in the shape of these leaves
Examples from the Corpus
trefoil• Bees hummed steadily through the yellow bird's foot trefoil that wove itself in a tangled carpet over the sand.Origin trefoil (1300-1400) Old French trefeuil, from Latin trifolium, from tri- “three” + folium “leaf” 