The Collaborative International Dictionary of English v.0.48:
Ether \E"ther\ ([=e]"th[~e]r), n. [L. aether, Gr. a'iqh`r, fr.
a'i`qein to light up, kindle, burn, blaze; akin to Skr. idh,
indh, and prob. to E. idle: cf. F. ['e]ther.] [Written also
1. (Physics) A medium of great elasticity and extreme
tenuity, once supposed to pervade all space, the interior
of solid bodies not excepted, and to be the medium of
transmission of light and heat; hence often called
luminiferous ether. It is no longer believed that such a
medium is required for the transmission of electromagnetic
waves; the modern use of the term is mostly a figurative
term for empty space, or for literary effect, and not
intended to imply the actual existence of a physical
medium. However. modern cosmological theories based on
quantum field theory do not rule out the possibility that
the inherent energy of the vacuum is greater than zero, in
which case the concept of an ether pervading the vacuum
may have more than metaphoric meaning.
[1913 Webster +PJC]
2. Supposed matter above the air; the air itself.
(a) A light, volatile, mobile, inflammable liquid,
(C2H5)2O, of a characteristic aromatic odor,
obtained by the distillation of alcohol with sulphuric
acid, and hence called also sulphuric ether. It is a
powerful solvent of fats, resins, and pyroxylin, but
finds its chief use as an an[ae]sthetic. Commonly
called ethyl ether to distinguish it from other
ethers, and also ethyl oxide.
(b) Any similar compound in which an oxygen atom is bound
to two different carbon atoms, each of which is part
of an organic radical; as, amyl ether; valeric ether;
methyl ethyl ether. The general formular for an ether
is ROR', in which R and R' are organic radicals
which may be of similar or different structure. If R
and R' are different parts of the same organic
radical, the structure forms a cyclic ether.
[1913 Webster +PJC]
Complex ether, Mixed ether (Chem.), an ether in which the
ether oxygen is attached to two radicals having different
structures; as, ethyl methyl ether, C2H5.O.CH3.
Compound ether (Chem.), an ethereal salt or a salt of some
hydrocarbon as the base; an ester.
Ether engine (Mach.), a condensing engine like a steam
engine, but operated by the vapor of ether instead of by