The Collaborative International Dictionary of English v.0.48:

Morass \Mo*rass"\, n. [OE. marras, mareis (perh. through D.
   moeras), fr. F. marais, prob. from L. mare sea, in LL., any
   body of water; but perh. influenced by some German word. See
   Mere a lake, and cf. Marsh.]
   A tract of soft, wet ground; a marsh; a fen.
   [1913 Webster]

   Morass ore. (Min.) See Bog ore, under Bog.
      [1913 Webster]

WordNet (r) 3.0 (2006):

morass
    n 1: a soft wet area of low-lying land that sinks underfoot
         [syn: mire, quagmire, quag, morass, slack]