quan·tal / ˈkwäntl/ • adj. technical composed of discrete units; varying in steps rather than continuously: a quantal release of neurotransmitter. ∎ Physics of or relating to a quantum or quanta, or to quantum theory. ∎ chiefly Physiol. relating to or denoting an all-or-none response or state.DERIVATIVES: quan·tal·ly / ˈkwäntl-ē/ adv.