The Collaborative International Dictionary of English v.0.48:

Neglect \Neg*lect"\, v. t. [imp. & p. p. Neglected; p. pr. &
   vb. n. Neglecting.] [L. neglectus, p. p. of neglegere
   (negligere) to disregard, neglect, the literal sense prob.
   being, not to pick up; nec not, nor (fr. ne not + -que, a
   particle akin to Goth. -h, -uh, and prob. to E. who; cf.
   Goth. nih nor) + L. legere to pick up, gather. See No,
   adv., Legend, Who.]
   1. Not to attend to with due care or attention; to forbear
      one's duty in regard to; to allow to pass unimproved,
      unheeded, undone, etc.; to omit; to disregard; to slight;
      as, to neglect duty or business; to neglect to pay debts.
      [1913 Webster]

            I hope
            My absence doth neglect no great designs. --Shak.
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            This, my long suffering and my day of grace,
            Those who neglect and scorn shall never taste.
                                                  --Milton.
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   2. To omit to notice; to forbear to treat with attention or
      respect; to slight; as, to neglect strangers.
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   Syn: To slight; overlook; disregard; disesteem; contemn. See
        Slight.
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The Collaborative International Dictionary of English v.0.48:

Neglect \Neg*lect"\, n. [L. neglectus. See Neglect, v.]
   1. Omission of proper attention; avoidance or disregard of
      duty, from heedlessness, indifference, or willfulness;
      failure to do, use, or heed anything; culpable disregard;
      as, neglect of business, of health, of economy.
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            To tell thee sadly, shepherd, without blame,
            Or our neglect, we lost her as we came. --Milton.
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   2. Omission of attention or civilities; slight; as, neglect
      of strangers.
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   3. Habitual carelessness; negligence.
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            Age breeds neglect in all.            --Denham.
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   4. The state of being disregarded, slighted, or neglected.
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            Rescue my poor remains from vile neglect. --Prior.
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   Syn: Negligence; inattention; disregard; disesteem;
        remissness; indifference. See Negligence.
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   benign neglect A deliberate policy of minimizing public
      discussion of a controversial issue [e.g. by the
      president] on the theory that excessive discussion in
      itself is harmful or counterproductive.
      [PJC]

WordNet (r) 3.0 (2006):

neglect
    n 1: lack of attention and due care [syn: disregard,
         neglect]
    2: the state of something that has been unused and neglected;
       "the house was in a terrible state of neglect" [syn:
       neglect, disuse]
    3: willful lack of care and attention [syn: disregard,
       neglect]
    4: the trait of neglecting responsibilities and lacking concern
       [syn: negligence, neglect, neglectfulness]
    5: failure to act with the prudence that a reasonable person
       would exercise under the same circumstances [syn:
       negligence, carelessness, neglect, nonperformance]
    v 1: leave undone or leave out; "How could I miss that typo?";
         "The workers on the conveyor belt miss one out of ten"
         [syn: neglect, pretermit, omit, drop, miss,
         leave out, overlook, overleap] [ant: attend to,
         take to heart]
    2: fail to do something; leave something undone; "She failed to
       notice that her child was no longer in his crib"; "The
       secretary failed to call the customer and the company lost
       the account" [syn: fail, neglect]
    3: fail to attend to; "he neglects his children"
    4: give little or no attention to; "Disregard the errors" [syn:
       neglect, ignore, disregard]