fluid

noun

1. (countable, uncountable)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.

   “An extreme version of vorticity is a vortex. The vortex is a spinning, cyclonic mass of fluid, which can be observed in the rotation of water going down a drain, as well as in smoke rings, tornados and hurricanes.”

2. (countable, uncountable)A liquid (as opposed to a solid or gas).

   “fluid inclusion Petrology, a tiny fluid- or gas-filled cavity in an igneous rock. 1-100 micrometers in diameter, formed by the entrapment of a fluid, typically that from which the rock crystallized.”

   “The Doctor: Get a good night's sleep and drink plenty of fluids. / Kes: Fluids? / The Doctor: Everybody should drink plenty of fluids.”

   “For studying interfaces between solid and another solid, fluid, or gas, a sample can be oriented with its reflecting surface(s) vertical (and with the scattering plane, as defined by nominal incident and reflected wavevectors, horizontal).”

   “Tenderness: is the lump tender? Composition: is the mass solid, fluid or gas?”

   “The choke manifold then expels the fluid or gas to the gas buster or a panic line. The panic line will then either send the fluid or gas to the reserve pit or a flare stack or flare tank.”

3. (colloquial, countable, specifically, uncountable)Intravenous fluids.

adj

1. (not-comparable)Of or relating to fluid.
2. In a state of flux; subject to change.

   “Economics is a messy discipline: too fluid to be a science, too rigorous to be an art. Perhaps it is fitting that economists’ most-used metric, gross domestic product (GDP), is a tangle too. GDP measures the total value of output in an economic territory. Its apparent simplicity explains why it is scrutinised down to tenths of a percentage point every month.”

3. Moving smoothly, or giving the impression of a liquid in motion.

   “Tom of the fluid pelvis, undulating about the living room in defiance of Michael's taboo on sensuality.”

4. Convertible into cash.
5. (rare)Genderfluid.

   “Oh, Loki made sure of that. My mortal parents blamed him for the way I was, for being fluid.”

   “As do renewals in genres such as romcoms and teen movies, which have updated sexist, heteronormative tropes to reflect audiences’ fluid, inclusive, queer realities.”