a shrub or small tree, Vitex agnus-castus, of southern Europe, having aromatic, hairy leaves and long clusters of fragrant, pale lilac-blue flowers. Also called hemp tree, monk's pepper tree .
[ 1555-65; trans. of L agnus castus, var. of AGNOS CASTUS (by influence of agnus lamb) ágnos kind of willow + L castus chaste, reinforcement of the idea thought to be in ágnos by confusion with Gk hagnós pure ]