Dictionary
Gei'ger count"er
an instrument for detecting ionizing radiations, consisting of a gas-filled tube in which electric-current pulses are produced when the gas is ionized by radiation, and of a device to register these pulses: used chiefly to measure radioactivity. Also called
Gei'ger-Mül'ler count"er. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.