The act of subverting; as overthrowing or destroying a legally constituted government WordNet 3.0 & Open English WordNet

Subversion refers to a Machiavellian process by which the values and principles of a system in place are contradicted or reversed in an attempt to sabotage the established social order and its structures of power, authority, tradition, hierarchy, and social norms. Wikipedia

Attempt to overthrow structures of authority. Wikipedia Disambiguation

A systematic attempt to overthrow a government by working from within; undermining. Wiktionary

Systematic attempt to overthrow a government by working from within. Wiktionary (translation)