Webster's Revised Unabridged Dictionary · 1913

Discoid

Discoid , adjective

[Greek {not transcribed} quoit-shaped, {not transcribed} a round plate, quoit + e'i^dos form, shape: compare French discoide. 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.
Collocations (1)
Discoid flower (Botany) , a compound flower, consisting of tubular florets only, as a tansy, lacking the rays which are seen in the daisy and sunflower.

Discoid , noun

Anything having the form of a discus or disk; particularly, a discoid shell.