zinnia vs old maid flower

zinnia and old maid flower both are nouns.

Word	Noun	Adjective	Verb	Adverb
zinnia	Yes	No	No	No
old maid flower	Yes	No	No	No

As nouns, zinnia and old maid flower are synonyms defined as:

zinnia and old maid flower: any of various plants of the genus Zinnia cultivated for their variously and brightly colored flower heads

Other synonyms of zinnia include old maid.

zinnia (noun)	old maid flower (noun)
any of various plants of the genus Zinnia cultivated for their variously and brightly colored flower heads	any of various plants of the genus Zinnia cultivated for their variously and brightly colored flower heads