n. A book containing either all or the principal words of a language, or words of one or more specified classes, arranged in a stated order, usually alphabetical, with definitions or explanations of their meanings and other information concerning them, expressed either in the same or in another language; a word-book; a lexicon; a vocabulary: as, an English dictionary; a Greek and Latin dictionary; a French-English or an English-French dictionary.n. Synonyms Glossary, Lexicon, etc. See vocabulary.Pertaining to or contained in a dictionary.