Althaea \Al*th[ae]"a\, Althea \Al*the"a\, n. [althaea, Gr. ?.] (Bot.) (a) A genus of plants of the Mallow family. It includes the officinal marsh mallow, and the garden hollyhocks. (b) An ornamental shrub ({Hibiscus Syriacus}) of the Mallow family. [1913 Webster]