Definition of "closed circuit" []

• An electric circuit providing an uninterrupted, endless path for the flow of current. (noun)
• A television transmission circuit with a limited number of reception stations and no broadcast facilities. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The gas-suit was tight and constricting, the closed circuit breathing apparatus cut into the back of my neck and the high concentration of oxygen made my mouth dry."