The Collaborative International Dictionary of English v.0.48:

Disagreement \Dis`a*gree"ment\ (d[i^]s`[.a]*gr[=e]"ment), n.
   [Cf. F. d['e]sagr['e]ment disagreeable circumstance,
   disagreeableness.]
   1. The state of disagreeing; a being at variance;
      dissimilitude; diversity.
      [1913 Webster]

   2. Unsuitableness; unadaptedness. [R.]
      [1913 Webster]

   3. Difference of opinion or sentiment.
      [1913 Webster]

   4. A falling out, or controversy; difference.

   Syn: Difference; diversity; dissimilitude; unlikeness;
        discrepancy; variance; dissent; misunderstanding;
        dissension; division; dispute; jar; wrangle; discord.
        [1913 Webster]

WordNet (r) 3.0 (2006):

disagreement
    n 1: a conflict of people's opinions or actions or characters
         [syn: disagreement, dissension, dissonance] [ant:
         accord, agreement]
    2: a difference between conflicting facts or claims or opinions;
       "a growing divergence of opinion" [syn: discrepancy,
       disagreement, divergence, variance]
    3: the speech act of disagreeing or arguing or disputing [ant:
       agreement]