| Noun | 1.horse cassia - East Indian tree having long pods containing a black cathartic pulp used as a horse medicineCassia marginata, Cassia roxburghiicassia - any of various trees or shrubs of the genus Cassia having pinnately compound leaves and usually yellow flowers followed by long seedpods | | 2.horse cassia - tropical American semi-evergreen tree having erect racemes of pink or rose-colored flowers; used as an ornamentalCassia grandis, pink shower, pink shower treecassia - any of various trees or shrubs of the genus Cassia having pinnately compound leaves and usually yellow flowers followed by long seedpods |