Geiger counter

UK: /ˈgaɪgə^rkaʊntə^r/ US: /ˈgaɪgɚ ˌkaʊntɚ/

WordReference Random House Learner's Dictionary of American English © 2025

Gei•ger count•er /ˈgaɪgɚ ˌkaʊntɚ/  n. [countable]

1. Physics an instrument for detecting certain radiation, used chiefly to measure radioactivity.

WordReference Random House Unabridged Dictionary of American English © 2025

Gei′ger count′er, 

1. Physics 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. 

• named after H. Geiger 1920–25

Collins Concise English Dictionary © HarperCollins Publishers::

Geiger counter, Geiger-Müller counter / ˈɡaɪɡəˈmʊlə/ noun

1. an instrument for detecting and measuring the intensity of ionizing radiation. It consists of a gas-filled tube containing a fine wire anode along the axis of a cylindrical cathode with a potential difference of several hundred volts. Any particle or photon which ionizes any number of gas molecules in the tube causes a discharge which is registered by electronic equipment. The magnitude of the discharge does not depend upon the nature or the energy of the ionizing particle

Etymology: 20th Century: named after Hans Geiger and W. Müller, 20th-century German physicist