Source : Webster's Revised Unabridged Dictionary (1913)

Quagmire \Quag"mire`\, n. [Quake + mire.]
   Soft, wet, miry land, which shakes or yields under the feet.
   ``A spot surrounded by quagmires, which rendered it difficult
   of access.'' --Palfrey.

   Syn: Morass; marsh; bog; swamp; fen; slough.

Source : WordNet®

quagmire
     n : a soft wet area of low-lying land that sinks underfoot [syn:
          {mire}, {quag}, {morass}]