The Collaborative International Dictionary of English v.0.48:

Latin \Lat"in\, a. [F., fr. L. Latinus belonging to Latium,
   Latin, fr. Latium a country of Italy, in which Rome was
   situated. Cf. Ladin, Lateen sail, under Lateen.]
   1. Of or pertaining to Latium, or to the Latins, a people of
      Latium; Roman; as, the Latin language.
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   2. Of, pertaining to, or composed in, the language used by
      the Romans or Latins; as, a Latin grammar; a Latin
      composition or idiom.
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   Latin Church (Eccl. Hist.), the Western or Roman Catholic
      Church, as distinct from the Greek or Eastern Church.

   Latin cross. See Illust. 1 of Cross.

   Latin races, a designation sometimes loosely given to
      certain nations, esp. the French, Spanish, and Italians,
      who speak languages principally derived from Latin.

   Latin Union, an association of states, originally
      comprising France, Belgium, Switzerland, and Italy, which,
      in 1865, entered into a monetary agreement, providing for
      an identity in the weight and fineness of the gold and
      silver coins of those countries, and for the amounts of
      each kind of coinage by each. Greece, Servia, Roumania,
      and Spain subsequently joined the Union.
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The Collaborative International Dictionary of English v.0.48:

Latin \Lat"in\, n.
   1. A native or inhabitant of Latium; a Roman.
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   2. The language of the ancient Romans.
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   3. An exercise in schools, consisting in turning English into
      Latin. [Obs.] --Ascham.
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   4. (Eccl.) A member of the Roman Catholic Church.
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   Dog Latin, barbarous Latin; a jargon in imitation of Latin;
      as, the log Latin of schoolboys.

   Late Latin, Low Latin, terms used indifferently to
      designate the latest stages of the Latin language; low
      Latin (and, perhaps, late Latin also), including the
      barbarous coinages from the French, German, and other
      languages into a Latin form made after the Latin had
      become a dead language for the people.

   Law Latin, that kind of late, or low, Latin, used in
      statutes and legal instruments; -- often barbarous.
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The Collaborative International Dictionary of English v.0.48:

Latin \Lat"in\, v. t.
   To write or speak in Latin; to turn or render into Latin.
   [Obs.] --Fuller.
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WordNet (r) 3.0 (2006):

Latin
    adj 1: of or relating to the ancient Latins or the Latin
           language; "Latin verb conjugations"
    2: relating to people or countries speaking Romance languages;
       "Latin America"
    3: relating to languages derived from Latin; "Romance languages"
       [syn: Romance, Latin]
    4: of or relating to the ancient region of Latium; "Latin towns"
    n 1: any dialect of the language of ancient Rome
    2: an inhabitant of ancient Latium
    3: a person who is a member of those peoples whose languages
       derived from Latin

Easton's 1897 Bible Dictionary:

Latin
   the vernacular language of the ancient Romans (John 19:20).