The Collaborative International Dictionary of English v.0.48:

Umbrage \Um"brage\ ([u^]m"br[asl]j; 48), n. [F. ombrage shade,
   suspicion, umbrage, L. umbraticus belonging to shade, fr.
   umbra a shade. Cf. Umber, Umbratic.]
   1. Shade; shadow; obscurity; hence, that which affords a
      shade, as a screen of trees or foliage.
      [1913 Webster]

            Where highest woods, impenetrable
            To star or sunlight, spread their umbrage broad.
                                                  --Milton.
      [1913 Webster]

   2. Shadowy resemblance; shadow. [Obs.]
      [1913 Webster]

            The opinion carries no show of truth nor umbrage of
            reason on its side.                   --Woodward.
      [1913 Webster]

   3. The feeling of being overshadowed; jealousy of another, as
      standing in one's light or way; hence, suspicion of injury
      or wrong; offense; resentment.
      [1913 Webster]

            Which gave umbrage to wiser than myself. --Evelyn.
      [1913 Webster]

            Persons who feel most umbrage from the overshadowing
            aristocracy.                          --Sir W.
                                                  Scott.
      [1913 Webster]

WordNet (r) 3.0 (2006):

umbrage
    n 1: a feeling of anger caused by being offended; "he took
         offence at my question" [syn: umbrage, offense,
         offence]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "umbrage":
   adumbration, angry look, annoyance, dark shade, dirty look,
   dudgeon, enrage, exasperation, foliage, foliation, frondage, frown,
   fury, glare, gloom, glower, huff, incense, infuriate, ire, irking,
   irritation, leafage, leafiness, mad, madden, mere shadow, miff,
   nettling, offense, penumbra, pique, provoking, rage, resentment,
   scowl, screen, shade, shadiness, shadow, shadows numberless,
   silhouette, skiagram, skiagraph, snuff, steam up, umbra,
   umbrageousness, verdure, vexation, wrath