Di″a‐dem (?), n. [F. diadème, L. diadema, fr. Gr. �, fr. � to bind round; διά through, across + � to bind; cf. Skr. dā to bind.] 1. Originally, an ornamental head band or fillet, worn by Eastern monarchs as a badge of royalty; hence (later), also, a crown, in general. “The regal diadem.” Milton.
2. Regal power; sovereignty; empire; — considered as symbolized by the crown.
3. (Her.) An arch rising from the rim of a crown (rarely also of a coronet), and uniting with others over its center.
Diadem lemur. (Zoöl.) See Indri. — Diadem spider(Zoöl.), the garden spider.