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]

The Collaborative International Dictionary of English v.0.48:

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).
       [1913 Webster]

WordNet (r) 3.0 (2006):

bluebell
    n 1: sometimes placed in genus Scilla [syn: wild hyacinth,
         wood hyacinth, bluebell, harebell, Hyacinthoides
         nonscripta, Scilla nonscripta]
    2: one of the most handsome prairie wildflowers having large
       erect bell-shaped bluish flowers; of moist places in prairies
       and fields from eastern Colorado and Nebraska south to New
       Mexico and Texas [syn: prairie gentian, tulip gentian,
       bluebell, Eustoma grandiflorum]
    3: perennial of northern hemisphere with slender stems and bell-
       shaped blue flowers [syn: harebell, bluebell, Campanula
       rotundifolia]