The Collaborative International Dictionary of English v.0.48:
Feather-foil \Feath"er-foil`\, n. [Feather + foil a leaf.] (Bot.) An aquatic plant (Hottonia palustris), having finely divided leaves. [1913 Webster]WordNet (r) 3.0 (2006):
feather-foil n 1: a plant of the genus Hottonia [syn: featherfoil, feather-foil]