American English

Definition of underground adverb from the Oxford Advanced American Dictionary

     

    underground

     adverb
    adverb
    NAmE//ˌʌndərˈɡraʊnd//
     
     
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  1. 1under the surface of the ground Rescuers found victims trapped several feet underground. toxic waste buried deep underground a network of pipelines running underground
  2. 2in or into a secret place in order to hide from the police, the government, etc. He went underground to avoid arrest.
See the Oxford Advanced Learner's Dictionary entry: underground