wallflower

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 ]

☞ 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. ]