wall‧flow‧er /ˈwɔːlˌflaʊə $ ˈwɒːlˌflaʊər/ noun [countable]

1. informal someone at a party, dance etc who is not asked to dance or take part in the activities

2. a sweet-smelling garden plant with yellow and red flowers

[TahlilGaran] Dictionary of Contemporary English ▲

wallflower
n. A girl who has to sit out dances because nobody is asking her to dance.
"I used to be a wallflower during my high school days," Valerie complained, "but my luck changed for better once I got into college."

[TahlilGaran] English Idioms Dictionary ▲