Meaning of cloud chamber

cloud' cham"ber

Pronunciation: [key]
— Physics. Physics.
  1. an apparatus for determining the movements of charged particles, consisting of a chamber containing a supersaturated mixture of gas and vapor, the vapor condensing around ions created by the particle in its passing, thereby revealing the path of the particle. Also calledCf. bubble chamber.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.