(not comparable) Of or relating to fluid. / In a state of flux; subject to change. / Moving smoothly, or giving the impression of a liquid in motion. / (of an asset) Convertible into cash.

Any substance which can flow with relative ease, tends to assume the shape of its container, and obeys Bernoulli's principle; a liquid, gas or plasma. / A liquid (as opposed to a solid or gas).

plural of fluid

The quality of being fluid.

plural of fluid ounce

Any of various units of volume used for liquid measure, all approximately 1.73–1.83 cubic inches or 28.4–30 milliliters.

(zoology) In placental mammals, a fluid contained within the amnion membrane that surrounds a developing embryo or fetus.

(mechanics) The branch of mechanics dealing with gases and liquids, either at rest or in motion.

(physics) A substance at a temperature and pressure above its own thermodynamic critical point that can diffuse through solids like a gas and dissolve materials like a liquid.

(humorous) A mythical automotive material used either in jokes or to gauge how inept someone is in basic auto mechanics.