Source : Webster's Revised Unabridged Dictionary (1913)

Gentian \Gen"tian\, n. [OE. genciane, F. gentiane, L. gentiana,
   fr. Gentius, an Illyrian king, said to have discovered its
   properties.] (Bot.)
   Any one of a genus ({Gentiana}) of herbaceous plants with
   opposite leaves and a tubular four- or five-lobed corolla,
   usually blue, but sometimes white, yellow, or red. See
   Illust. of {Capsule}.

   Note: Many species are found on the highest mountains of
         Europe, Asia, and America, and some are prized for
         their beauty, as the Alpine ({Gentiana verna},
         {Bavarica}, and {excisa}), and the American fringed
         gentians ({G. crinita} and {G. detonsa}). Several are
         used as tonics, especially the bitter roots of
         {Gentiana lutea}, the officinal gentian of the
         pharmacop[oe]ias.

   {Horse gentian}, fever root.

   {Yellow gentian} (Bot.), the officinal gentian ({Gentiana
      lutea}). See {Bitterwort}.

Source : WordNet®

gentian
     n : any of various plants of the family Gentianaceae especially
         the genera Gentiana and Gentianella and Gentianopsis