1 : a coloring material (obtained from lichens) that turns red in acid solutions and blue in alkaline solutions; used as a very rough acid-base indicator
2 : any plant of the genus Helianthus having large flower heads with dark disk florets and showy yellow rays
3 : any plant of the genus Helianthus having large flower heads with dark disk florets and showy yellow rays
4 : any plant of the genus Helianthus having large flower heads with dark disk florets and showy yellow rays
5 : any plant of the genus Helianthus having large flower heads with dark disk florets and showy yellow rays
