noun, plural cost·mar·ies. a composite plant, Chrysanthemum balsamita, that has silvery, fragrant leaves and is used in salads and as a flavoring.
Also called mint geranium.
Origin:
1325–75; Middle English costmarie, equivalent to cost (Old English cost costmary < Latin costum, costus a composite herb, Saussurea lappa < Greek kóstos) + Marie (the Virgin) Mary