n. & adj.
--n.
1. any leguminous plant of the genus Trifolium, with leaves of three leaflets and flowers of various colours, esp. clover.
2 any plant with similar leaves.
3 a three-lobed ornamentation, esp. in tracery windows.
4 a thing arranged in or with three lobes.
--adj. of or concerning a three-lobed plant, window tracery, etc.
Derivatives:
trefoiled adj. (also in comb.).
Etymology: ME f. AF trifoil f. L trifolium (as TRI-, folium leaf)