This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. A device consisting of a piston that moves within a cylinder containing oil, used to dampen and control motion.

n. A mechanical damping device consisting of a piston that moves through a viscous fluid (usually oil); used, in conjunction with a spring, in shock absorbers

n. a mechanical damping device containing a piston that moves in a fluid-filled chamber to serve as a pneumatic or hydraulic cushion for a falling weight, as in the valve gear of a steam engine, to prevent shock.

n. A cylinder containing a loosely fitted piston, and partly filled with fluid, designed to check sudden movements in a piece of mechanism to which it is attached.

n. A device sometimes used for controlling the motion of an arc-lamp, and in other electrical instruments.

n. a mechanical damper; the vibrating part is attached to a piston that moves in a chamber filled with liquid

"Yep, let's see, cart attached to wall with a spring, a pendulum attached to the cart, a force applied to the end of the pendulum, and a dashpot between the pendulum and the wall."

dash-pot   

damper    muffler