wallflower

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of numerous herbs of the genus Erysimum of the mustard family, having fragrant yellow, orange, or brownish flowers.
2. n. Any of several perennial herbs of the genus Cheiranthus, especially C. cheiri.
3. n. One who does not participate in the activity at a social event because of shyness or unpopularity.
4. n. A security, company, or industry that is out of favor with investors.

Century Dictionary and Cyclopedia

1. n. An old favorite garden flower and pot-plant, Cheiranthus Cheiri, native in southern Europe, where it grows on old walls, cliffs, and the sides of quarries. The flowers have four petals, with a spreading limb on long claws, colored a deep-orange, or in cultivation varying from pale-yellow to deep-red, are clustered in short racemes, and are sweet-scented. It is grown in many varieties, classed as single and double biennials and double perennials. It grows by preference upon walls, forming there an enduring bush, but may be planted on rocky banks, and is also one of the finest of border-plants. It formerly shared the name of heart's-ease; and in western England a dark-red variety is called bleeding-heart. A common name also is gilly-flower, or, for distinction, wall-gillyflower. The nameis extended to other species of the genus and to some species of Erysimum.
2. n. A man or woman who, at a ball or party, sits by the wall, or looks on without dancing, either from choice or from being unable to dance or to obtain a partner.

Wiktionary

1. n. Several short-lived herbs or shrubs of the Erysimum genus with bright yellow to red flowers.
2. n. informal A person who is socially awkward, especially one who does not dance at a party due to shyness.

GNU Webster's 1913

1. n. (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.
2. n. colloq. A lady at a ball, who, either from choice, or because not asked to dance, remains a spectator.
3. n. (Bot.) In Australia, the desert poison bush (Gastrolobium grandiflorum); -- called also native wallflower.

WordNet 3.0

1. n. 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
2. n. any of numerous plants of the genus Erysimum having fragrant yellow or orange or brownish flowers
3. n. remains on sidelines at social event