Source : Webster's Revised Unabridged Dictionary (1913)

Valerian \Va*le"ri*an\, n. [LL. valeriana, perhaps from some
   person named Valerius, or fr. L. valere to be strong.
   powerful, on account of its medicinal virtues: cf. F.
   val['e]riane.] (Bot.)
   Any plant of the genus {Valeriana}. The root of the officinal
   valerian ({V. officinalis}) has a strong smell, and is much
   used in medicine as an antispasmodic.

   {Greek valerian} (Bot.), a plant ({Polemonium c[ae]ruleum})
      with blue or white flowers, and leaves resembling those of
      the officinal valerian.

Source : WordNet®

valerian
     n : a plant of the genus Valeriana having lobed or dissected
         leaves and cymose white or ink flowers