\Flu"id\, 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.

\Flu"id\, n.
A fluid substance; a body whose particles move easily among
themselves.
Note: Fluid is a generic term, including liquids and gases as
      species. Water, air, and steam are fluids. By analogy,
      the term is sometimes applied to electricity and
      magnetism, as in phrases electric fluid, magnetic
      fluid, though not strictly appropriate.
{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.