Definition of fucoid

• a. - Properly, belonging to an order of alga: (Fucoideae) which are blackish in color, and produce oospores which are not fertilized until they have escaped from the conceptacle. The common rockweeds and the gulfweed (Sargassum) are fucoid in character.
• a. - In a vague sense, resembling seaweeds, or of the nature of seaweeds.
• n. - A plant, whether recent or fossil, which resembles a seaweed. See Fucoid, a.