Source : Webster's Revised Unabridged Dictionary (1913)

Feather-foil \Feath"er-foil`\, n. [Feather + foil a leaf.]
   (Bot.)
   An aquatic plant ({Hottonia palustris}), having finely
   divided leaves.

Source : WordNet®

feather-foil
     n : a plant of the genus Hottonia [syn: {featherfoil}]