Fucus \Fu"cus\, 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.]

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

Note: Formerly most marine alg? were called fuci.

Source: Webster's Revised Unabridged Dictionary (1913)