a perennial marsh plant (Acorus calamus) of the arum family, with sword-shaped leaves, small, green flowers, and a sweet-scented rhizome
See sweet flag in American Heritage Dictionary 4
noun
A hardy perennial herb (Acorus calamus) of the Northern Hemisphere, growing in marshy places and having grasslike leaves, minute greenish flowers borne on a thick spadix, and aromatic rhizomes. Also called calamus.