Found 1 definition: agnus castus.
[CIDE DICTIONARY]
agnus castus, [Gr. a willowlike tree, used at a religious festival; confused with holy, chaste.].
A species of Vitex (Vitex agnus castus); the chaste tree. Loudon. [1913 Webster]
"And wreaths of agnus castus others bore." [1913 Webster]
[RELATED WORDS]
agnus, agnus dei, agnus scythicus