\Syn"o*nym\, n.
1. An incorrect or incorrectly applied scientific name, as a
   new name applied to a species or genus already properly
   named, or a specific name preoccupied by that of another
   species of the same genus; -- so used in the system of
   nomenclature (which see) in which the correct scientific
   names of certain natural groups (usually genera, species,
   and subspecies) are regarded as determined by priority.
2. One of two or more words corresponding in meaning but of
   different languages; a heteronym. [Rare]

\Syn"o*nym\ (s[i^]n"[-o]*n[i^]m), n.; pl. {Synonyms}
(-n[i^]mz). [F. synonyme, L. synonyma, pl. of synonymum, Gr.
synw`nymon. See {Synonymous}.]
One of two or more words (commonly words of the same
language) which are equivalents of each other; one of two or
more words which have very nearly the same signification, and
therefore may often be used interchangeably. See under
{Synonymous}. [Written also {synonyme}.]
      All languages tend to clear themselves of synonyms as
      intellectual culture advances, the superfluous words
      being taken up and appropriated by new shades and
      combinations of thought evolved in the progress of
      society.                                 --De Quincey.
      His name has thus become, throughout all civilized
      countries, a synonym for probity and philanthropy.
                                               --Macaulay.
      In popular literary acceptation, and as employed in
      special dictionaries of such words, synonyms are words
      sufficiently alike in general signification to be
      liable to be confounded, but yet so different in
      special definition as to require to be distinguished.
--G. P. Marsh.