a. [ad. mod.L. spīroīdēs (cf. Gr. σπειροειδῶς spirally), f. spīra SPIRE sb.3: see -OID. So F. spiroïde.] Tending to a spiral form.
1849. Herschel, Outl. Astron., 468. It would be easy … to trace … the form of the spiroid curve.
1859. Mayne, Expos. Lex., 1190/1. Spiroides,… resembling a screw: spiroid.
