Source : Webster's Revised Unabridged Dictionary (1913)

Serene \Se*rene"\, n.
   1. Serenity; clearness; calmness. [Poetic.] ``The serene of
      heaven.'' --Southey.

            To their master is denied To share their sweet
            serene.                               --Young.

   2. [F. serein evening dew or damp. See {Serein}.] Evening
      air; night chill. [Obs.] ``Some serene blast me.'' --B.
      Jonson.

Serene \Se*rene"\, v. t. [L. serenare.]
   To make serene.

         Heaven and earth, as if contending, vie To raise his
         being, and serene his soul.              --Thomson.

Serene \Se*rene"\, a. [L. serenus to grow dry, Gr. ??? hot,
   scorching.]
   1. Bright; clear; unabscured; as, a serene sky.

            The moon serene in glory mounts the sky. --Pope.

            Full many a gem of purest ray serene The dark
            unfathomed caves of ocean bear.       --Gray.

   2. Calm; placid; undisturbed; unruffled; as, a serene aspect;
      a serene soul. --Milton.

   Note: In several countries of Europe, Serene is given as a
         tittle to princes and the members of their families;
         as, His Serene Highness.

   {Drop serene}. (Med.) See {Amaurosis}. --Milton.

Source : WordNet®

serene
     adj 1: characterized by absence of emotional agitation; "calm
            acceptance of the inevitable"; "remained serene in the
            midst of turbulence"; "a serene expression on her
            face"; "she became more tranquil"; "tranquil life in
            the country" [syn: {calm}, {tranquil}]
     2: completely clear and fine; "serene skies and a bright blue
        sea"