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Meaning of master cylinder

mas'ter cyl'inder

Pronunciation: [key]
  1. the hydraulic pump of an automotive braking system that contains a cylinder and one or two pistons, is actuated by the brake pedal, and supplies hydraulic fluid under pressure to the brakes at each wheel.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.