Microcoustic \Mi`cro*cous"tic\, a. [Micro- + acoustic: cf. F. microcoustique, micracoustique.] Pertaining, or suited, to the audition of small sounds; fitted to assist hearing. Microcoustic \Mi`cro*cous"tic\, n. An instrument for making faint sounds audible, as to a partially deaf person.