Source : Webster's Revised Unabridged Dictionary (1913)

Encyclopedia \En*cy`clo*pe"di*a\, Encyclopaedia
\En*cy`clo*p[ae]"di*a\, n. [NL., fr. Gr. ?, for ? ?, instruction
   in the circle of arts and sciences: cf. F. encyclop['e]die.
   See {Cyclopedia}, and {Encyclical}.] [Formerly written
   {encyclop[ae]dy} and {encyclopedy}.]
   The circle of arts and sciences; a comprehensive summary of
   knowledge, or of a branch of knowledge; esp., a work in which
   the various branches of science or art are discussed
   separately, and usually in alphabetical order; a cyclopedia.

Source : WordNet®

encyclopaedia
     n : a reference work (often in several volumes) containing
         articles on various topics (often arranged in
         alphabetical order) dealing with the entire range of
         human knowledge or with some particular specialty [syn: {encyclopedia},
          {cyclopedia}, {cyclopaedia}]