Pronunciation: '&n-d&r-"
Function: noun
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.