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.

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.

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

Source: Webster's Revised Unabridged Dictionary (1913)