hydraulic fluid

American  

noun

1. a fluid, usually of low viscosity, as oil, used in a hydraulic system.

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Etymology

Origin of hydraulic fluid

First recorded in 1940–45

Example Sentences

Airbus and Boeing, the two biggest aircraft manufacturers, have acknowledged that malfunctions can lead to oil and hydraulic fluid leaking into the engines or power units and vaporizing at extreme heat.

From The Wall Street Journal • Sep. 14, 2025

René Descartes believed that animal spirits flowed from the brain through hollow nerves and inflated the muscles, just as hydraulic fluid traveled through machines in the royal gardens at Saint-Germain.

From Scientific American • Apr. 9, 2022

Internal documents from airlines and aircraft manufacturers provide detailed instructions for identifying oil and hydraulic fluid contamination in the air supply by smells like “dirty socks,” “musty” and “acrid,” The Times found.

From Los Angeles Times • Mar. 31, 2022

Pilots practice how to deal with such an event frequently and would have immediately shut off anything flammable in the engine, including fuel and hydraulic fluid, using a single switch, Cox said.

From Seattle Times • Feb. 20, 2021

This would produce changes in the pressure of the hydraulic fluid by affecting the kinetic energy of the fluid's atoms.

From Tom Swift and The Visitor from Planet X by Appleton, Victor [pseud.]