Source : Webster's Revised Unabridged Dictionary (1913)

Bluebell \Blue"bell`\, n. (Bot.)
   (a) A plant of the genus {Campanula}, especially the
       {Campanula rotundifolia}, which bears blue bell-shaped
       flowers; the harebell.
   (b) A plant of the genus {Scilla} ({Scilla nutans}).

Harebell \Hare"bell`\, n. (Bot.)
   A small, slender, branching plant ({Campanula rotundifolia}),
   having blue bell-shaped flowers; also, {Scilla nutans}, which
   has similar flowers; -- called also {bluebell}. [Written also
   {hairbell}.]

         E'en the light harebell raised its head. --Sir W. Scott
                                                  .

Source : WordNet®

Campanula rotundifolia
     n : perennial of northern hemisphere with slender stems and
         bell-shaped blue flowers [syn: {harebell}, {bluebell}]