Source : Webster's Revised Unabridged Dictionary (1913)

Vesper \Ves"per\, n. [L., the evening, the evening star, the
   west; akin to Gr. ?, ?, and perhaps to E. west. Cf.
   {Hesperian}, {Vespers}.]
   The evening star; Hesper; Venus, when seen after sunset;
   hence, the evening. --Shak.

Vesper \Ves"per\, a.
   Of or pertaining to the evening, or to the service of
   vespers; as, a vesper hymn; vesper bells.

   {Vesper sparrow}, the grass finch. See under {Grass}.

Evening \E"ven*ing\, n. [AS. [=ae]fnung. See {even}, n., and cf.
   {Eve}.]
   1. The latter part and close of the day, and the beginning of
      darkness or night; properly, the decline of the day, or of
      the sum.

            In the ascending scale Of heaven, the stars that
            usher evening rose.                   --Milton.

   Note: Sometimes, especially in the Southern parts of the
         United States, the afternoon is called evening.
         --Bartlett.

   2. The latter portion, as of life; the declining period, as
      of strength or glory.

   Note: Sometimes used adjectively; as, evening gun. ``Evening
         Prayer.'' --Shak.

   {Evening flower} (Bot.), a genus of iridaceous plants
      ({Hesperantha}) from the Cape of Good Hope, with
      sword-shaped leaves, and sweet-scented flowers which
      expand in the evening.

   {Evening grosbeak} (Zo["o]l.), an American singing bird
      ({Coccothraustes vespertina}) having a very large bill.
      Its color is olivaceous, with the crown, wings, and tail
      black, and the under tail coverts yellow. So called
      because it sings in the evening.

   {Evening primrose}. See under {Primrose}.

   {The evening star}, the bright star of early evening in the
      western sky, soon passing below the horizon; specifically,
      the planet Venus; -- called also {Vesper} and {Hesperus}.
      During portions of the year, Mars, Jupiter, and Saturn are
      also evening stars. See {Morning Star}.

Source : WordNet®

Vesper
     n 1: a planet (usually Venus) seen at sunset in the western sky
          [syn: {evening star}, {Hesperus}]
     2: a late afternoon or evening worship service