The Collaborative International Dictionary of English v.0.48:

Fender \Fen"der\, n. [From Fend, v. t. & i., cf. Defender.]
   One who or that which defends or protects by warding off
   harm; as:
   (a) A screen to prevent coals or sparks of an open fire from
       escaping to the floor.
   (b) Anything serving as a cushion to lessen the shock when a
       vessel comes in contact with another vessel or a wharf.
   (c) A screen to protect a carriage from mud thrown off the
       wheels: also, a splashboard.
   (d) Anything set up to protect an exposed angle, as of a
       house, from damage by carriage wheels.
       [1913 Webster]

WordNet (r) 3.0 (2006):

fender
    n 1: a barrier that surrounds the wheels of a vehicle to block
         splashing water or mud; "in Britain they call a fender a
         wing" [syn: fender, wing]
    2: an inclined metal frame at the front of a locomotive to clear
       the track [syn: fender, buffer, cowcatcher, pilot]
    3: a low metal guard to confine falling coals to a hearth
    4: a cushion-like device that reduces shock due to an impact
       [syn: buffer, fender]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "fender":
   aegis, arm guard, backstop, barrier, brattice, buffer,
   buffer state, bulkhead, bulwark, bumper, chimney, chimney corner,
   cloison, collision mat, contraceptive, copyright, crash helmet,
   cushion, dashboard, diaphragm, dissepiment, dividing line,
   dividing wall, division, dodger, face mask, finger guard,
   fire screen, fireboard, fireguard, fireplace, fireside, flue,
   foot guard, fuse, goggles, governor, guard, guardrail, hand guard,
   handrail, hard hat, hearth, hearthstone, helmet, hob, hub, ingle,
   inglenook, ingleside, insulation, interlock, interseptum,
   knee guard, knuckle guard, laminated glass, life preserver,
   lifeline, lightning conductor, lightning rod, mask, mat, midriff,
   midsection, mudguard, nose guard, pad, padding, palladium, panel,
   paries, partition, party wall, patent, pilot, preventive,
   property line, prophylactic, protective clothing,
   protective umbrella, safeguard, safety, safety glass, safety plug,
   safety rail, safety shoes, safety switch, safety valve, screen,
   seat belt, separation, septulum, septum, shield, shin guard,
   shock pad, smokehole, sun helmet, umbrella, wall, windscreen,
   windshield