Meaning of ACOUSTIC in English

a ‧ cous ‧ tic /əˈkuːstɪk/ BrE AmE adjective

[ Date: 1700-1800 ; Language: Greek ; Origin: akoustikos 'of hearing' , from akouein 'to hear' ]

1 . relating to sound and the way people hear things

2 . an acoustic ↑ guitar or other musical instrument does not have its sound made louder electronically ⇨ electric

—acoustically /-kli/ adverb

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.