The Collaborative International Dictionary of English v.0.48:

Lex \Lex\ (l[e^]ks), n.; pl. Leges (l[=e]"j[=e]z). [L. See
   Legal.]
   Law; as, lex talionis, the law of retaliation; lex terr[ae],
   the law of the land; lex fori, the law of the forum or court;
   lex loci, the law of the place; lex mercatoria, the law or
   custom of merchants.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "lex":
   act, bill, bylaw, canon, decree, dictate, dictation, edict,
   enactment, form, formality, formula, formulary, institution, jus,
   law, legislation, measure, ordinance, ordonnance, prescript,
   prescription, regulation, rubric, rule, ruling, standing order,
   statute



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

Lex

   1.  A lexical analyser generator for Unix and its
   input language.  There is a GNU version called flex and a
   version written in, and outputting, SML/NJ called ML-lex.
   A version, by David Poole at Montana has been retargeted to
   Turbo Pascal, (ftp://iecc.com/pub/file/lyprg.zip).

   ["Lex - A Lexical Analyzer Generator", M.E. Lesk, CS TR 39,
   Bell Labs, Oct 1975].

   2.  The lexical specification
   language for COPS.

   ["Metalanguages of the Compiler Production System COPS",
   J. Borowiec, in GI Fachgesprach "Compiler-Compiler", ed
   W. Henhapl, Tech Hochs Darmstadt 1978, pp.122-159].

   (2000-11-15)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

LEX. The law. A law for the government of mankind in society. Among the
ancient Romans, this word was frequently used as synonymous with right, jus.
When put absolutely, lex meant the Law of the Twelve Tables.