The Collaborative International Dictionary of English v.0.48:

Erroneous \Er*ro"ne*ous\, a. [L. erroneus, fr. errare to err.
   See Err.]
   1. Wandering; straying; deviating from the right course; --
      hence, irregular; unnatural. [Obs.] "Erroneous
      circulation." --Arbuthnot.
      [1913 Webster]

            Stopped much of the erroneous light, which otherwise
            would have disturbed the vision.      --Sir I.
                                                  Newman.
      [1913 Webster]

   2. Misleading; misled; mistaking. [Obs.]
      [1913 Webster]

            An erroneous conscience commands us to do what we
            ought to omit.                        --Jer. Taylor.
      [1913 Webster]

   3. Containing error; not conformed to truth or justice;
      incorrect; false; mistaken; as, an erroneous doctrine;
      erroneous opinion, observation, deduction, view, etc. --
      Er*ro"ne*ous*ly, adv. -- Er*ro"ne*ous*ness, n.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

erroneousness \erroneousness\ n.
   inadvertent incorrectness.

   Syn: error.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

erroneousness
    n 1: inadvertent incorrectness [syn: erroneousness, error]