Entry 2 senses · 2 variants Webster, 1913 Microcoustic · Mi·cro·cous·tic · IPA a. n. 01 a. Pertaining, or suited, to the audition of small sounds; fitted to assist hearing. 1. Pertaining, or suited, to the audition of small sounds; fitted to assist hearing. 02 n. An instrument for making faint sounds audible, as to a partially deaf person. 1. An instrument for making faint sounds audible, as to a partially deaf person.