a malvaceous plant, Althaea officinalis, that grows in salt marshes and has pale pink flowers. The roots yield a mucilage formerly used to make marshmallows
2. US and Canadian another name for rose mallow (sense 1)
marsh mallow in American English
1.
a pink-flowered, perennial, European plant (Althaea officinalis) of the mallow family: the root was formerly used for marshmallows and is sometimes used in medicine