fen

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Low, flat, swampy land; a bog or marsh.

Century Dictionary and Cyclopedia

1. n. Low land covered wholly or partially with water, but producing sedge, coarse grasses, or other aquatic plants; boggy land; a bog; a marsh: as, the bogs in Ireland, or the fens in Lincolnshire, Kent, and Cambridgeshire, England.
2. n. Mud; mire.
3. n. A disease affecting hops, caused by a quick-growing moss or mold. Imp. Dict. Synonyms Swamp, etc. See marsh.
4. To forbid: same as fend : used in this form by boys in marbles and other games, in an exclamatory way, to check or block, according to understood rules, some move of an opposing player. It occurs in such phrases as “fen roundings!”— that is, I forbid moving around in a circle (as a player might otherwise do in order to avoid some obstruction), “fen dubs!”— that is, I forbid doubles (said when a player knocks two marbles out of the ring, one of which must then be put back). The phrase is properly used only by the opposing player, but through ignorance of its real meaning it may be used also by the player who knocks the marbles out, who thereby cuts off the opponent's right to object, and pockets both marbles.
5. n. A section in the work of the Arabic physician Avicenna, called the Canon.

Wiktionary

1. n. A type of wetland fed by ground water and runoff, containing peat below the waterline.
2. n. A plural form of fan used by enthusiasts of science fiction, fantasy, and anime, partly from whimsy and partly to distinguish themselves from fans of sport, etc.

GNU Webster's 1913

1. n. Low land overflowed, or covered wholly or partially with water, but producing sedge, coarse grasses, or other aquatic plants; boggy land; moor; marsh.

WordNet 3.0

1. n. low-lying wet land with grassy vegetation; usually is a transition zone between land and water
2. n. 100 fen equal 1 yuan in China