Fucus

n.; pl. Fuci [ L. rock lichen, orchil, used as a red dye, red or purple color, disguise, deceit. ] 1. A paint; a dye; also, false show. [ Obs. ] [ 1913 Webster ]

2. (Bot.) A genus of tough, leathery seaweeds, usually of a dull brownish green color; rockweed. [ 1913 Webster ]

☞ Formerly most marine algæ were called fuci. [ 1913 Webster ]