The Collaborative International Dictionary of English v.0.48:

Grammar \Gram"mar\, v. i.
   To discourse according to the rules of grammar; to use
   grammar. [Obs.] --Beau. & Fl.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Grammar \Gram"mar\, n. [OE. gramere, OF. gramaire, F. grammaire
   Prob. fr. L. gramatica Gr ?, fem. of ? skilled in grammar,
   fr. ? letter. See Gramme, Graphic, and cf. Grammatical,
   Gramarye.]
   1. The science which treats of the principles of language;
      the study of forms of speech, and their relations to one
      another; the art concerned with the right use and
      application of the rules of a language, in speaking or
      writing.
      [1913 Webster]

   Note: The whole fabric of grammar rests upon the classifying
         of words according to their function in the sentence.
         --Bain.
         [1913 Webster]

   2. The art of speaking or writing with correctness or
      according to established usage; speech considered with
      regard to the rules of a grammar.
      [1913 Webster]

            The original bad grammar and bad spelling.
                                                  --Macaulay.
      [1913 Webster]

   3. A treatise on the principles of language; a book
      containing the principles and rules for correctness in
      speaking or writing.
      [1913 Webster]

   4. treatise on the elements or principles of any science; as,
      a grammar of geography.
      [1913 Webster]

   Comparative grammar, the science which determines the
      relations of kindred languages by examining and comparing
      their grammatical forms.

   Grammar school.
      (a) A school, usually endowed, in which Latin and Greek
          grammar are taught, as also other studies preparatory
          to colleges or universities; as, the famous Rugby
          Grammar School. This use of the word is more common in
          England than in the United States.
          [1913 Webster]

                When any town shall increase to the number of a
                hundred
                families or householders, they shall set up a
                grammar school, the master thereof being able to
                instruct youth so far as they may be fitted for
                the University.                   --Mass.
                                                  Records
                                                  (1647).
      (b) In the American system of graded common schools, at
          one time the term referred to an intermediate school
          between the primary school and the high school, in
          which the principles of English grammar were taught;
          now, it is synonymous with primary school or
          elementary school, being the first school at which
          children are taught subjects required by the state
          educational laws. In different communities, the
          grammar school (primary school) may have grades 1 to
          4, 1 to 6, or 1 to 8, usually together with a
          kindergarten. Schools between the primary school and
          high school are now commonly termed middle school or
          intermediate school.
          [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

grammar
    n 1: the branch of linguistics that deals with syntax and
         morphology (and sometimes also deals with semantics)

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "grammar":
   abecedarium, abecedary, alphabet, alphabet book, basics,
   battledore, bowwow theory, casebook, choice of words,
   comparative linguistics, composition, derivation,
   descriptive linguistics, dialect, dialectology, diction,
   dingdong theory, elements, etymology, exercise book, expression,
   first principles, first steps, formulation, fundamentals,
   glossematics, glossology, glottochronology, glottology, gradus,
   graphemics, historical linguistics, hornbook, idiom, induction,
   language, language study, lexicology, lexicostatistics,
   linguistic geography, linguistic science, linguistics, locution,
   manual, manual of instruction, mathematical linguistics,
   morphology, morphophonemics, outlines, paleography, parlance,
   philology, phonetics, phonology, phrase, phraseology, phrasing,
   primer, principia, principles, psycholinguistics, reader, rhetoric,
   rudiments, schoolbook, semantics, sociolinguistics, speech,
   speller, spelling book, structuralism, syntactics, t, talk, text,
   transformational linguistics, usage, use of words, usus loquendi,
   verbiage, wordage, wording, workbook



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

grammar

    A formal definition of the syntactic structure (the
   syntax) of a language.

   A grammar is normally represented as a set of production
   rules which specify the order of constituents and their
   sub-constituents in a sentence (a well-formed string in the
   language).  Each rule has a left-hand side symbol naming a
   syntactic category (e.g. "noun-phrase" for a natural
   language grammar) and a right-hand side which is a sequence
   of zero or more symbols.  Each symbol may be either a
   terminal symbol or a non-terminal symbol.  A terminal symbol
   corresponds to one "lexeme" - a part of the sentence with no
   internal syntactic structure (e.g. an identifier or an
   operator in a computer language).  A non-terminal symbol is
   the left-hand side of some rule.

   One rule is normally designated as the top-level rule which
   gives the structure for a whole sentence.

   A parser (a kind of recogniser) uses a grammar to parse a
   sentence, assigning a terminal syntactic category to each
   input token and a non-terminal category to each appropriate
   group of tokens, up to the level of the whole sentence.
   Parsing is usually preceded by lexical analysis.  The
   opposite, generation, starts from the top-level rule and
   chooses one alternative production wherever there is a choice.

   In computing, a formal grammar, e.g. in BNF, can be used to
   parse a linear input stream, such as the source code of a
   program, into a data structure that expresses the (or a)
   meaning of the input in a form that is easier for the computer
   to work with.  A compiler compiler like yacc might be used
   to convert a grammar into code for the parser of a compiler.
   A grammar might also be used by a transducer, a translator
   or a syntax directed editor.

   See also attribute grammar.

   (2009-02-06)


The Devil's Dictionary (1881-1906):

GRAMMAR, n.  A system of pitfalls thoughtfully prepared for the feet
for the self-made man, along the path by which he advances to
distinction.