from
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.]