- a person who, because of shyness, unpopularity, or lack of a partner, remains at the side at a party or dance.
- any person, organization, etc., that remains on or has been forced to the sidelines of any activity: The firm was a wallflower in this year's bidding for government contracts.
- a European plant, Cheiranthus cheiri, of the mustard family, that, when growing wild on walls, cliffs, etc., has sweet-scented, usually yellow or orange flowers, but when cultivated has flowers varying in color from pale yellow to brown-red or purple.
- any of several related plants of the genera Cheiranthus and Erysimum.
- a plant, Cheiranthus cheiri, of S Europe, grown for its clusters of yellow, orange, brown, red, or purple fragrant flowers and naturalized on old walls, cliffs, etc: family Brassicaceae (crucifers)
- any of numerous other crucifers of the genera Cheiranthus and Erysimum, having orange or yellow flowers
- a person who stays on the fringes of a dance or party on account of lacking a partner or being shy
