political opposition vs underground

political opposition

noun
  • Actions by one political group against another political group, either by using governmental power or by popular actions such as protests; generally, disagreement in politics. 

  • A recognized political party or group of parties in multiparty political systems that is present in Parliament or some other legislative body and does not control the floor (usually due to being in the minority). 

  • An unrecognized political party in a one-party state. 

underground

noun
  • A movement or organisation of people who resist political convention. 

  • A movement or organisation of people who resist artistic convention. 

  • Regions beneath the surface of the earth, both natural (eg. caves) and man-made (eg. mines). 

  • Synonym of subway: a railway that is under the ground. 

adj
  • Hidden, furtive, secretive. 

  • Below the ground; below the surface of the Earth. 

  • Outside the mainstream, especially unofficial and hidden from the authorities. 

adv
  • Below the ground. 

  • Secretly. 

verb
  • To route electricity distribution cables underground. 

How often have the words political opposition and underground occurred in a corpus of books? (source: Google Ngram Viewer )