Discoid \Dis"coid\, a. [Gr. ? quoit-shaped, ? a round plate, quoit + ? form, shape: cf. F. disco["i]de. See {Disk}.] Having the form of a disk, as those univalve shells which have the whorls in one plane, so as to form a disk, as the pearly nautilus. {Discoid flower} (Bot.), a compound flower, consisting of tubular florets only, as a tansy, lacking the rays which are seen in the daisy and sunflower.