Origin of underground

First recorded in 1565–75; under- + ground1

Example sentences from the Web for underground

British Dictionary definitions for underground

underground

adjective (ˈʌndəˌɡraʊnd)

occurring, situated, or used below ground level an underground tunnel; an underground explosion
secret; hidden underground activities

adverb (ˌʌndəˈɡraʊnd)

going below ground level the tunnel led underground
into hiding or secrecy the group was driven underground

noun (ˈʌndəˌɡraʊnd)