The Collaborative International Dictionary of English v.0.48:

Vivacious \Vi*va"cious\ (?; 277), a. [L. v['i]vax, -acis, fr.
   vivere to live. See Vivid.]
   1. Having vigorous powers of life; tenacious of life;
      long-lived. [Obs.]
      [1913 Webster]

            Hitherto the English bishops have been vivacious
            almost to wonder. . . . But five died for the first
            twenty years of her [Queen Elizabeth's] reign.
                                                  --Fuller.
      [1913 Webster]

            The faith of Christianity is far more vivacious than
            any mere ravishment of the imagination can ever be.
                                                  --I. Taylor.
      [1913 Webster]

   2. Sprightly in temper or conduct; lively; merry; as, a
      vivacious poet. "Vivacious nonsense." --V. Knox.
      [1913 Webster]

   3. (Bot.) Living through the winter, or from year to year;
      perennial. [R.]
      [1913 Webster]

   Syn: Sprightly; active; animated; sportive; gay; merry;
        jocund; light-hearted.
        [1913 Webster] -- Vi*va"cious*ly, adv. --
        Vi*va"cious*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

vivacious
    adj 1: vigorous and animated; "a vibrant group that challenged
           the system"; "a charming and vivacious hostess"; "a
           vivacious folk dance" [syn: vibrant, vivacious]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "vivacious":
   active, activist, activistic, acute, aggressive, agog, alacritous,
   alert, alive, all agog, animate, animated, antic, anxious, avid,
   blithe, bouncing, bouncy, breathless, breezy, brisk, bubbly,
   buoyant, bursting to, cant, capersome, cheerful, chipper, coltish,
   desirous, dynamic, eager, ebullient, effervescent, energetic,
   enterprising, enthusiastic, exuberant, forceful, forcible, forward,
   frisky, frolicsome, full of beans, full of go, full of life,
   full of pep, gamesome, gay, go-go, happy, hearty, high-spirited,
   impatient, impetuous, incisive, intense, jaunty, keen, kinetic,
   light-hearted, live, lively, living, lusty, mercurial, merry,
   mettlesome, militant, panting, peppy, perky, pert, piquant,
   playful, poignant, prompt, pungent, quick, quicksilver, racy,
   raring to, ready, ready and willing, robust, rollicking,
   rollicksome, rompish, skittish, smacking, snappy, spanking,
   sparkling, spirited, sportive, sprightly, spry, strenuous, strong,
   sunny, take-charge, take-over, trenchant, up, vibrant, vigorous,
   vital, vivid, zestful, zesty, zingy, zippy