The Collaborative International Dictionary of English v.0.48:

Overlook \O`ver*look"\, v. t. [imp. & p. p. Overlooked; p. pr.
   & vb. n. Overlooking.]
   1. To look down upon from a place that is over or above; to
      look over or view from a higher position; to be situated
      above, so as to command a view of; as, to overlook a
      valley from a hill; a hotel room that overlooks the
      marketplace. "The pile o'erlooked the town." --Dryden.
      [1913 Webster +PJC]

            [Titan] with burning eye did hotly overlook them.
                                                  --Shak.
      [1913 Webster]

   2. Hence: To supervise; to watch over; sometimes, to observe
      secretly; as, to overlook a gang of laborers; to overlook
      one who is writing a letter.
      [1913 Webster]

   3. To inspect; to examine; to look over carefully or
      repeatedly. "Overlook this pedigree." --Shak.
      [1913 Webster]

            The time and care that are required
            To overlook and file and polish well. --Roscommon.
      [1913 Webster]

   4. To look upon with an evil eye; to bewitch by looking upon;
      to fascinate. [Obs. or Prov. Eng.] --Shak.
      [1913 Webster]

            If you trouble me I will overlook you, and then your
            pigs will die.                        --C. Kingsley.
      [1913 Webster]

   5. To look over and beyond (anything) without seeing it; to
      miss or omit in looking; to fail to notice; to fail to
      observe; as, to overlook a mistake in addition; to
      overlook a missing bolt.
      [1913 Webster +PJC]

   6. Hence: To refrain from bestowing notice or attention upon;
      to disregard or deliberately ignore; to pass over without
      censure or punishment; to excuse or pardon (a fault,
      error, or misdeed).
      [1913 Webster +PJC]

            The times of ignorance therefore God overlooked.
                                                  --Acts xvii.
                                                  30 (Rev. Ver.
                                                  )
      [1913 Webster]

            They overlook truth in the judgments they pass.
                                                  --Atterbury.
      [1913 Webster]

            The pardoning and overlooking of faults. --Addison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

overlooked
    adj 1: not taken into account; "his retirement was not allowed
           to go unmarked" [syn: overlooked, unmarked,
           unnoted]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "overlooked":
   abandoned, absolved, acquitted, blotted, canceled, condoned,
   deserted, disregarded, exculpated, excused, exonerated, forgiven,
   forgotten, half-done, ignored, indulged, laid aside, left undone,
   missed, neglected, omitted, pardoned, passed by, passed over,
   passed up, pigeonholed, put aside, redeemed, remitted, reprieved,
   shriven, shunted, sidelined, sidetracked, slighted, spared,
   unasked, unattended to, unavenged, uncared-for, unchaperoned,
   uncondemned, unconsidered, undone, unregarded, unresented,
   unrevenged, unsolicited, untended, unwatched, wiped away