folium

n.; pl. E. Foliums L. Folia [ L., a leaf. ] 1. A leaf, esp. a thin leaf or plate. [ 1913 Webster ]

2. (Geom.) A curve of the third order, consisting of two infinite branches, which have a common asymptote. The curve has a double point, and a leaf-shaped loop; whence the name. Its equation is x3 + y3 = axy. [ 1913 Webster ]