The Collaborative International Dictionary of English v.0.48:

Harebell \Hare"bell`\ (h[^a]r"b[e^]l`), 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.]
   [1913 Webster]

         E'en the light harebell raised its head. --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

harebell
    n 1: sometimes placed in genus Scilla [syn: wild hyacinth,
         wood hyacinth, bluebell, harebell, Hyacinthoides
         nonscripta, Scilla nonscripta]
    2: perennial of northern hemisphere with slender stems and bell-
       shaped blue flowers [syn: harebell, bluebell, Campanula
       rotundifolia]