The Collaborative International Dictionary of English v.0.48:

Madden \Mad"den\, v. t. [imp. & p. p. Maddened; p. pr. & vb.
   n. Maddening.]
   1. To make mad; to drive to madness; to drive to insanity; to
      craze.
      [1913 Webster]

   2. To make very angry; to enrage; to excite violently with
      passion.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

maddening \maddening\ adj.
   extremely annoying or displeasing.

   Syn: annoying, exasperating, infuriating, vexing.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

maddening
    adj 1: extremely annoying or displeasing; "his cavelier curtness
           of manner was exasperating"; "I've had an exasperating
           day"; "her infuriating indifference"; "the ceaseless
           tumult of the jukebox was maddening" [syn:
           exasperating, infuriating, maddening, vexing]