noun. Any of various perennial herbs of the genus Arnica in the composite family, having opposite, simple leaves and yellow or orange flower heads.

noun. A tincture of the dried flower heads of the European species A. montana, applied externally to reduce the pain and inflammation of bruises and sprains.

noun. Any of several plants, of the genus Arnica, related to the sunflowers.

"The arnica is diluted so much that there is only one molecule of it per 7 million billion billion billion billion pills."