Source : Webster's Revised Unabridged Dictionary (1913)

Fen \Fen\, n. [AS. fen, fenn, marsh, mud, dirt; akin to D. veen,
   OFries. fenne, fene, OHG. fenna, G. fenn, Icel. fen, Goth.
   fani mud.]
   Low land overflowed, or covered wholly or partially with
   water, but producing sedge, coarse grasses, or other aquatic
   plants; boggy land; moor; marsh.

         'Mid reedy fens wide spread.             --Wordsworth.

   Note: Fen is used adjectively with the sense of belonging to,
         or of the nature of, a fen or fens.

   {Fen boat}, a boat of light draught used in marshes.

   {Fen duck} (Zo["o]l.), a wild duck inhabiting fens; the
      shoveler. [Prov. Eng.]

   {Fen fowl} (Zo["o]l.), any water fowl that frequent fens.

   {Fen goose} (Zo["o]l.), the graylag goose of Europe. [Prov.
      Eng.]

   {Fen land}, swamp land.

Source : WordNet®

fen
     n 1: 100 fen equal 1 yuan
     2: low-lying wet land with grassy vegetation; usually is a
        transition zone between land and water; "thousands of
        acres of marshland"; "the fens of eastern England" [syn: {marsh},
         {marshland}, {fenland}]