Milfoil \Mil"foil\, n. [F. mille-feuille, L. millefolium; mille thousand + folium leaf. See Foil a leaf.]

(Bot.) A common composite herb (Achillea Millefolium) with white flowers and finely dissected leaves; yarrow.

Water milfoil (Bot.), an aquatic herb with dissected leaves (Myriophyllum).

Source: Webster's Revised Unabridged Dictionary (1913)