Source : Webster's Revised Unabridged Dictionary (1913)

Err \Err\, v. i. [imp. & p. p. {Erred}; p. pr. & vb. n. {Erring}
   (?; 277, 85).] [F. errer, L. errare; akin to G. irren, OHG.
   irran, v. t., irr?n, v. i., OS. irrien, Sw. irra, Dan. irre,
   Goth, a['i]rzjan to lead astray, airzise astray.]
   1. To wander; to roam; to stray. [Archaic] ``Why wilt thou
      err from me?'' --Keble.

            What seemeth to you, if there were to a man an
            hundred sheep and one of them hath erred. --Wyclif
                                                  (Matt. xviii.
                                                  12).

   2. To deviate from the true course; to miss the thing aimed
      at. ``My jealous aim might err.'' --Shak.

   3. To miss intellectual truth; to fall into error; to mistake
      in judgment or opinion; to be mistaken.

            The man may err in his judgment of circumstances.
                                                  --Tillotson.

   4. To deviate morally from the right way; to go astray, in a
      figurative sense; to do wrong; to sin.

            Do they not err that devise evil?     --Prov. xiv.
                                                  22.

   5. To offend, as by erring.

Source : WordNet®

erring
     adj : capable of making an error; "all men are error-prone" [syn:
           {error-prone}]