WordNet (r) 3.0 (2006):

lexeme
    n 1: a minimal unit (as a word or stem) in the lexicon of a
         language; `go' and `went' and `gone' and `going' are all
         members of the English lexeme `go'

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "lexeme":
   antonym, articulation, expression, free form, glosseme, homograph,
   homonym, homophone, icon, lexical form, linguistic form, locution,
   logos, metonym, minimum free form, monosyllable, morpheme, phrase,
   polysyllable, semasiological unit, sememe, sign, signifiant,
   significant, syllable, symbol, synonym, term, token, type, usage,
   utterance, verbalism, verbum, vocable, word



The Free On-line Dictionary of Computing (30 December 2018):

lexeme

    A minimal lexical unit of a language.  Lexical
   analysis converts strings in a language into a list of
   lexemes.  For a programming language these word-like pieces
   would include keywords, identifiers, literals and
   punctuation.  The lexemes are then passed to the parser for
   syntactic analysis.

   (1996-04-06)