costmary, n. [L. costum an Oriental aromatic plant (Gr. , cf. Ar. kost, kust) + Maria Mary. Cf. Alecost.].
A garden plant (Chrysanthemum Balsamita) having a strong balsamic smell, and nearly allied to tansy. It is used as a pot herb and salad plant and in flavoring ale and beer. Called also alecost. [1913 Webster]