Definition of "circuit breaker" []

• An automatic switch that stops the flow of electric current in a suddenly overloaded or otherwise abnormally stressed electric circuit. (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.

• "For example, the outer knob of an ascent engine-arming circuit breaker broke off, which Buzz was able to depress prior to liftoff with a felt-tipped pen."