underground

I. adverb Date: 14th century 1. beneath the surface of the earth 2. in or into hiding or secret operation II. noun Date: 1594 1. a subterranean space or channel 2. an underground city railway system 3. a. a movement or group organized in strict secrecy among citizens especially in an occupied country for maintaining communications, popular solidarity, and concerted resistive action pending liberation b. a clandestine conspiratorial organization set up for revolutionary or other disruptive purposes especially against a civil order c. an unofficial, unsanctioned, or illegal but informal movement or group; especially a usually avant-garde group or movement that functions outside the establishment III. adjective Date: 1601 1. being, growing, operating, or situated below the surface of the ground 2. conducted by secret means 3. a. existing outside the establishment <

an underground literary reputation

> b. existing outside the purview of tax collectors or statisticians <

the underground economy

> 4. a. produced or published outside the establishment especially by the avant-garde <

underground movies

> <

underground newspapers

> b. of or relating to the avant-garde underground <

an underground moviemaker

> <

an underground theater

>