The Collaborative International Dictionary of English v.0.48:

Gillyflower \Gil"ly*flow`er\, n. [OE. gilofre, gilofer, clove,
   OF. girofre, girofle, F. girofle: cf. F. girofl['e]e
   gillyflower, fr. girofle, Gr. ? clove tree; ? nut + ? leaf,
   akin to E. foliage. Cf. Caryophyllus, July-flower.]
   [Written also gilliflower.] (Bot.)
   1. A name given by old writers to the clove pink (Dianthus
      Caryophyllus) but now to the common stock (Matthiola
      incana), a cruciferous plant with showy and fragrant
      blossoms, usually purplish, but often pink or white.
      [1913 Webster]

   2. A kind of apple, of a roundish conical shape, purplish red
      color, and having a large core.

   Clove gillyflower, the clove pink.

   Marsh gillyflower, the ragged robin (Lychnis
      Flos-cuculi).

   Queen's gillyflower, or Winter gillyflower, damewort.

   Sea gillyflower, the thrift (Armeria vulgaris).

   Wall gillyflower, the wallflower (Cheiranthus Cheiri).

   Water gillyflower, the water violet.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wallflower \Wall"flow`er\, n.
   1. (Bot.) A perennial, cruciferous plant (Cheiranthus
      Cheiri), with sweet-scented flowers varying in color from
      yellow to orange and deep red. In Europe it very common on
      old walls.
      [1913 Webster]

   Note: The name is sometimes extended to other species of
         Cheiranthus and of the related genus Erysimum,
         especially the American Western wallflower (Erysimum
         asperum), a biennial herb with orange-yellow flowers.
         [1913 Webster]

   2. A lady at a ball, who, either from choice, or because not
      asked to dance, remains a spectator. [Colloq.]
      [1913 Webster]

   3. (Bot.) In Australia, the desert poison bush (Gastrolobium
      grandiflorum); -- called also native wallflower.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Cheiranthus cheiri
    n 1: perennial of southern Europe having clusters of fragrant
         flowers of all colors especially yellow and orange; often
         naturalized on old walls or cliffs; sometimes placed in
         genus Erysimum [syn: wallflower, Cheiranthus cheiri,
         Erysimum cheiri]