zin·ni·a (zĭn'ē-ə) n. Any of various plants of the genus Zinnia, native to tropical America, especially Z. elegans, widely cultivated for its showy, rayed, variously colored flower heads. Also called regionally old maid, old maid flower.
[New Latin Zinnia, genus name, after Johann Gottfried Zinn (1727-1759), German botanist.]