undeˈliverable,a. (un-1 7 b.) In recent use esp. of postal matter, as in quot. 1862. 1843Carlyle Past & Pr. ii. xvii, Fix thyself in Dandyhood, undeliverable: it is thy doom.1862Trollope N. Amer. II. 388 The task of returning to their writers undelivered and undeliverable letters.