The Collaborative International Dictionary of English v.0.48:

Negligence \Neg"li*gence\, n. [F. n['e]gligence, L.
   negligentia.]
   The quality or state of being negligent; lack of due
   diligence or care; omission of duty; habitual neglect;
   heedlessness.
   [1913 Webster]

   2. An act or instance of negligence or carelessness.
      [1913 Webster]

            remarking his beauties, . . . I must also point out
            his negligences and defects.          --Blair.
      [1913 Webster]

   3. (Law) The omission of the care usual under the
      circumstances, being convertible with the Roman culpa. A
      specialist is bound to higher skill and diligence in his
      specialty than one who is not a specialist, and liability
      for negligence varies acordingly.
      [1913 Webster]

   Contributory negligence. See under Contributory.
      [1913 Webster]

   Syn: Neglect; inattention; heedlessness; disregard; slight.

   Usage: Negligence, Neglect. These two words are freely
          interchanged in our older writers; but a distinction
          has gradually sprung up between them. As now generally
          used, negligence is the habit, and neglect the act, of
          leaving things undone or unattended to. We are
          negligent as a general trait of character; we are
          guilty of neglect in particular cases, or in reference
          to individuals who had a right to our attentions.
          [1913 Webster]

WordNet (r) 3.0 (2006):

negligence
    n 1: failure to act with the prudence that a reasonable person
         would exercise under the same circumstances [syn:
         negligence, carelessness, neglect, nonperformance]
    2: the trait of neglecting responsibilities and lacking concern
       [syn: negligence, neglect, neglectfulness]

Moby Thesaurus II by Grady Ward, 1.0:

170 Moby Thesaurus words for "negligence":
   absentmindedness, accidia, acedia, allowance, apathy,
   approximation, ataraxia, ataraxy, bad policy, blowziness,
   carelessness, casualness, chintziness, culpa, culpable negligence,
   default, delinquency, dereliction, detachment, deviation,
   disconformity, disinterest, dispassion, disregard,
   disregardfulness, distraction, dowdiness, easiness, easygoingness,
   failing, failure, fecklessness, flightiness, flippancy,
   forgetfulness, frivolousness, frowziness, frumpishness, giddiness,
   grubbiness, hastiness, heedlessness, impolicy, impotence,
   imprecision, improvidence, inaccuracy, inaccurateness,
   inadvertence, inadvertency, inattention, inattentiveness,
   inconsideration, incorrectness, incuriosity, indifference,
   indiscrimination, inexactitude, inexactness, inexcitability,
   inexpedience, inexpediency, inobservance, insouciance, laches,
   lack of affect, lackadaisicalness, laissez-faire, lapse,
   lax stewardship, laxity, laxness, leniency, levity,
   lightmindedness, listlessness, looseness, loosening,
   maladministration, malfeasance, malpractice, messiness,
   mindlessness, misadministration, misconduct, misdirection,
   misfeasance, misgovernment, misguidance, mishandling,
   mismanagement, misrule, neglect, neglectfulness, nonadherence,
   nonchalance, noncompliance, nonconformance, nonconformity,
   nonfeasance, nonfulfillment, noninterference, nonobservance,
   nonperformance, nonrestriction, obliviousness, omission, oscitancy,
   overindulgence, overlooking, overpermissiveness, oversight,
   permissiveness, pococurantism, poor husbandry, poor stewardship,
   predictable error, probable error, procrastination, recklessness,
   regardlessness, relaxation, relaxedness, remissness, seediness,
   shabbiness, shallowness, shiftlessness, shoddiness, slackness,
   slatternliness, slight, slipshodness, sloppiness, sloth,
   slovenliness, slovenry, sluttishness, softness, sordidness,
   squalidness, squalor, standard deviation, superficiality,
   tackiness, tawdriness, thoughtlessness, thriftlessness, tolerance,
   unalertness, unanxiousness, unawareness, unconcern,
   unconsciousness, uncorrectness, unfactualness, unheedfulness,
   unintentiveness, unmindfulness, unneatness, unobservance,
   unpreciseness, unrestraint, unrigorousness, unsolicitousness,
   untidiness, unwariness, unwatchfulness, weakness, wrongdoing



Bouvier's Law Dictionary, Revised 6th Ed (1856):

NEGLIGENCE, contracts, torts. When considered in relation, to contracts,
negligence may be divided into various degrees, namely, ordinary, less than
ordinary, more than ordinary. 1 Miles' Rep. 40.
     2. Ordinary negligence is the want of ordinary diligence; slight or
less than ordinary negligence, is, the want of great diligence; and gross
or more than ordinary negligence, is the want of slight diligence.
     3. Three great principles of responsibility, seem naturally to follow
this division.
     4.-1. In those contracts which are made for the sole benefit of the
creditor, the debtor is responsible only for gross negligence, good faith
alone being required of him; as in tile case of a depositary, who is a
bailee without reward; Story, Bailm. 62; Dane's Ab. c. 17, a, 2; 14 Serg. &
Rawle, 275; but to this general rule, Pothier makes two exceptions. The
first, in relation to the contract of a mandate, and the second, to the
quasi contract negotiorum gestorum; in these cases, he says, the party
undertaking to perform these engagements, is bound to use necessary care.
Observation Generale, printed at the end of the Traite des Obligations.
     5.-2. In those contracts which are for the reciprocal benefit of both
parties, such as those of sale, of hiring, of pledge, and the like, the
party is bound to take, for the object of the contract, that care which a
prudent man ordinarily takes of his affairs, and he will therefore be held
responsible for ordinary neglect. Jones' Bailment, 10, 119; 2 Lord Raym.
909; Story, Bailm. Sec. 23; Pothier, Obs. Gener. ubi supra.
     6.-3. In those contracts made for the sole interest of the party who
has received, and is to return the thing which is the object of the
contract, such, for example, as loan for use, or commodatum, the slightest
negligence will make him responsible. Jones' Bailm. 64, 65; Story's Bailm.
Sec. 237; Pothier, Obs. Gen. ubi supra.
     7. In general, a party who has caused an injury or loss to another in
consequence of his negligence, is responsible for all the consequence. Hob.
134; 3 Wils. 126; 1  Chit. TI. 129, 130; 2 Hen. & Munf. 423; 1 Str. 596; 3
East, R. 596. An example of this kind may be found in the case of a person
who drives his carriage during a dark night on the wrong side of the road,
by which he commits an injury to another. 3 East, R. 593; 1 Campb. R. 497; 2
Cam b. 466; 2 New Rep. 119. Vide Gale and Whatley on Easements, Index, h.t.;
6 T. R. 659; 1 East, R. 106; 4 B. & A; 590; S. C. 6 E. C. L. R. 628; 1
Taunt. 568; 2 Stark. R. 272; 2 Bing. R. 170; 5 Esp. R. 35, 263; 5 B. & C.
550. Whether the incautious conduct of the plaintiff will excuse the
negligence of the defendant, see 1 Q. B. 29; 4 P. & D. 642; 3 M. Lyr. & Sc.
9; Fault.
     8. When the law imposes a duty on an officer, whether it be by common
law or statute, and he neglects to perform it, he may be indicted for such
neglect; 1 Salk. R. 380; 6 Mod, R. 96; and in some cases such neglect will
amount to a forfeiture of the office. 4 Bl. Com. 140. See Bouv. Inst. Index,
h.t.