/kost"mair'ee, kawst"-/ , n. , pl. costmaries .
a composite plant, Chrysanthemum balsamita, that has silvery, fragrant leaves and is used in salads and as a flavoring. Also called mint geranium .
[ 1325-75; ME costmarie, equiv. to cost (OE cost costmary costum, costus a composite herb, Saussurea lappa kóstos ) + Marie (the Virgin) Mary ]