from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; a liquid or gas.
  • adjective Of, relating to, or characteristic of a fluid.
  • adjective Readily reshaped; pliable.
  • adjective Smooth and flowing; graceful.
  • adjective Changing or tending to change; variable.
  • adjective Characterized by or allowing social mobility.
  • adjective Convertible into cash.

from The Century Dictionary.

  • Capable of flowing; liquid or gaseous; consisting of a substance incapable of resisting forces (tangential stresses) tending to change its shape.
  • Not fixed or rigid; flowing; shifting; fluent.
  • noun A substance which flows or is capable of flowing; a substance which is incapable of resisting forces (tangential stresses) tending to change its shape without altering its size.
  • noun Some hypothetical supersensible substance conceived as analogous to known fluids. See fluidism.
  • noun See the adjectives.
  • noun See the adjectives.

from the GNU version of the Collaborative International Dictionary of English.

  • noun A fluid substance; a body whose particles move easily among themselves.
  • noun a measure of capacity equal to one eighth of a fluid ounce.
  • noun In England, a measure of capacity equal to the twentieth part of an imperial pint. For water, this is the weight of the avoirdupois ounce, or 437.5 grains.
  • noun (Physiol.) The circulating blood and lymph, the chyle, the gastric, pancreatic, and intestinal juices, the saliva, bile, urine, aqueous humor, and muscle serum are the more important fluids of the body. The tissues themselves contain a large amount of combined water, so much, that an entire human body dried in vacuo with a very moderate degree of heat gives about 66 per cent of water.
  • noun See under Burning, Elastic, etc.
  • adjective Having particles which easily move and change their relative position without a separation of the mass, and which easily yield to pressure; capable of flowing; liquid or gaseous.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

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

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective in cash or easily convertible to cash
  • noun a substance that is fluid at room temperature and pressure
  • noun continuous amorphous matter that tends to flow and to conform to the outline of its container: a liquid or a gas
  • adjective subject to change; variable
  • adjective affording change (especially in social status)
  • adjective characteristic of a fluid; capable of flowing and easily changing shape
  • adjective smooth and unconstrained in movement


from The American Heritage® Dictionary of the English Language, 4th Edition

[From Middle English, flowing, from Old French fluide, from Latin fluidus, from fluere, to flow; see bhleu- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin fluidus ("flowing, fluid"), from fluere ("to flow"), akin to Ancient Greek φλύειν (fluein, "to swell, overflow"). Several related terms in English from Latin (fluent, flux), and cognate from Proto-Indo-European (via Germanic) with flow.


Help support Wordnik (and make this page ad-free) by adopting the word fluid.



Log in or sign up to get involved in the conversation. It's quick and easy.

  • Add to this everything that rhymes with fluid: druid, pluid, fruid, squid.

    September 7, 2010

  • There once was a venturesome druid

    who craved a dominion more fluid

    than forest or lea,

    so he jumped in the sea

    and was eaten alive by a squid.

    September 7, 2010

  • Oh, man! You made me laugh so hard that ink came out of my nose.

    September 7, 2010