Ra`di*om"e*ter (-&obreve;m"&esl;*t&etilde;r), n. [L. radius radius + -meter: cf. F. radiomètre.] 1. (Naut.) A forestaff.

2. (Physics) An instrument designed for measuring the mechanical effect of radiant energy.

&fist; It consists of a number of light disks, blackened on one side, placed at the ends of extended arms, supported on a pivot in an exhausted glass vessel. When exposed to rays of light or heat, the arms rotate.