a. [ L. fluidus, fr. fluere to flow: cf. F. fluide. See Fluent. ] 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. [ 1913 Webster ]

n. A fluid substance; a body whose particles move easily among themselves. [ 1913 Webster ]

☞ Fluid is a generic term, including liquids and gases as species. Water, air, and steam are fluids. By analogy, the term was sometimes applied to electricity and magnetism, as in phrases electric fluid, magnetic fluid, though not strictly appropriate; such usage has disappeared. [ 1913 Webster +PJC ]

Fluid dram, or
Fluid drachm, a measure of capacity equal to one eighth of a fluid ounce. --
Fluid ounce. (a) In the United States, a measure of capacity, in apothecaries' or wine measure, equal to one sixteenth of a pint or 29.57 cubic centimeters. This, for water, is about 1.04158 ounces avoirdupois, or 455.6 grains. (b) 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. --
Fluids of the body. (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. --
Burning fluid,
Elastic fluid,
Electric fluid,
Magnetic fluid, etc. See under Burning, Elastic, etc. [ 1913 Webster ]

a. Pertaining to a fluid, or to its flowing motion. [ 1913 Webster ]

Fluidal structure (Geol.), the structure characteristic of certain volcanic rocks in which the arrangement of the minute crystals shows the lines of flow of thew molten material before solidification; -- also called fluxion structure. [ 1913 Webster ]

n. [ Cf. F. fluidité. ] The quality of being fluid or capable of flowing; a liquid, aëriform, or gaseous state; -- opposed to solidity. [ 1913 Webster ]

It was this want of organization, this looseness and fluidity of the new movement, that made it penetrate through every class of society. J. R. Green. [ 1913 Webster ]

v. t. [ imp. & p. p. Fluidized p. pr. & vb. n. Fluidizing. ] To render fluid. [ 1913 Webster ]

n. The state of being fluid; fluidity. [ 1913 Webster ]

n. See Fluid ounce, under Fluid. [ 1913 Webster ]

n. See Fluid dram, under Fluid. Pharm. of the U. S. [ 1913 Webster ]