Source : Webster's Revised Unabridged Dictionary (1913)

Almanac \Al"ma*nac\ (?; 277), n. [LL. almanac, almanach: cf. F.
   almanach, Sp. almanaque, It. almanacco, all of uncertain
   origin.]
   A book or table, containing a calendar of days, and months,
   to which astronomical data and various statistics are often
   added, such as the times of the rising and setting of the sun
   and moon, eclipses, hours of full tide, stated festivals of
   churches, terms of courts, etc.

   {Nautical almanac}, an almanac, or year book, containing
      astronomical calculations (lunar, stellar, etc.), and
      other information useful to mariners.

Source : WordNet®

almanac
     n 1: an annual publication including weather forecasts and other
          miscellaneous information arranged according to the
          calendar of a given year [syn: {farmer's calendar}]
     2: an annual publication containing tabular information in a
        particular field or fields arranged according to the
        calendar of a given year