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]