The Collaborative International Dictionary of English v.0.48:

minefield \minefield\ n.
   1. (Mil.) a region in which explosive mines[4] have been
      placed, especially a region on land.
      [WordNet 1.5]

   2. Hence: (Fig.) A situation in which a simple mistake can
      have disastrous consequences; a touchy or dangerous
      situation requiring great caution; as, the candidate
      threaded his way skillfully through a minefield of loaded
      questions from the audience.
      [PJC]

WordNet (r) 3.0 (2006):

minefield
    n 1: a region in which explosives mines have been placed