Cost"ma*ry (k?st"m?-r?), n. [L. costum an Oriental aromatic plant (Gr. , cf. Ar. kost, kust) + Maria Mary. Cf.Alecost.] Bot.
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.
© Webster 1913.