The Collaborative International Dictionary of English v.0.48:

Ephemeris \E*phem"e*ris\, n.; pl. Ephemerides. [L., a diary,
   Gr. ?, also, a calendar, fr. ?. See Ephemera.]
   1. A diary; a journal. --Johnson.
      [1913 Webster]

   2. (Anat.)
      (a) A publication giving the computed places of the
          heavenly bodies for each day of the year, with other
          numerical data, for the use of the astronomer and
          navigator; an astronomical almanac; as, the "American
          Ephemeris and Nautical Almanac."
      (b) Any tabular statement of the assigned places of a
          heavenly body, as a planet or comet, on several
          successive days.
          [1913 Webster]

   3. (Literature) A collective name for reviews, magazines, and
      all kinds of periodical literature. --Brande & C.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ephemeris
    n 1: an annual publication containing astronomical tables that
         give the positions of the celestial bodies throughout the
         year; "today computers calculate the ephemerides"