acoustic

/əˈkuːstɪk/
/əˈkuːstɪk/

noun

  1. A medicine or other agent to assist hearing.

adjective

  1. Pertaining to the sense of hearing, the organs of hearing, or the science of sounds; auditory.

  2. Naturally producing or produced by an instrument without electrical amplification, as an acoustic guitar or acoustic piano.

noun

  1. (retronym) A hollow-body guitar of the older variety, in contradistinction to an electric guitar.