a. [ Fucus + -oid. ] (Bot.) (a) Properly, belonging to an order of alga: (Fucoideæ) which are blackish in color, and produce oöspores which are not fertilized until they have escaped from the conceptacle. The common rockweeds and the gulfweed (Sargassum) are fucoid in character. (b) In a vague sense, resembling seaweeds, or of the nature of seaweeds. [ 1913 Webster ]

n. (Bot.) A plant, whether recent or fossil, which resembles a seaweed. See Fucoid, a. [ 1913 Webster ]

a. 1. (Bot.) Fucoid. [ 1913 Webster ]

2. (Geol.) Containing impressions of fossil fucoids or seaweeds; as, fucoidal sandstone. [ 1913 Webster ]