Pronunciation: (rā"dē-om'i-tur), [key]
1. Also called Crookes radiometer. an instrument for demonstrating the transformation of radiant energy into mechanical work, consisting of an exhausted glass vessel containing vanes that revolve about an axis when exposed to light.
2. an instrument for detecting and measuring small amounts of radiant energy.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.