The Collaborative International Dictionary of English v.0.48:

Idleness \I"dle*ness\, n. [AS. [imac]delnes.]
   The condition or quality of being idle (in the various senses
   of that word); uselessness; fruitlessness; triviality;
   inactivity; laziness.

   Syn: Inaction; indolence; sluggishness; sloth.
        [1913 Webster]

WordNet (r) 3.0 (2006):

idleness
    n 1: having no employment [syn: idleness, idling, loafing]
    2: the quality of lacking substance or value; "the
       groundlessness of their report was quickly recognized" [syn:
       groundlessness, idleness]
    3: the trait of being idle out of a reluctance to work [syn:
       faineance, idleness]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "idleness":
   a wise passiveness, big deal, cautiousness, circumspection,
   contemplation, contemplative life, creeping, dawdling,
   deliberateness, deliberation, do-nothing policy, do-nothingism,
   do-nothingness, dolce far niente, dormancy, drawl, emptiness,
   flimsiness, foolishness, foot-dragging, frivolity, frivolousness,
   futility, idle hands, idle hours, immobility, inaction, inactivity,
   inanity, indolence, inertia, inertness, inoccupation,
   laissez-aller, laissez-faire, laissez-faireism, languor, lassitude,
   laze, laziness, lazing, leisureliness, lentitude, lentor, lethargy,
   levity, lightness, loafing, lollygagging, malingering, meditation,
   neutralism, neutrality, neutralness, noninvolvement,
   nonparticipation, nonresistance, nonviolence,
   nonviolent resistance, nugacity, otiosity, pacifism, paralysis,
   passive resistance, passive self-annihilation, passiveness,
   passivism, passivity, pokiness, policy, procrastination,
   quiescence, quietism, reluctance, shallowness, shiftlessness,
   shilly-shallying, shirking, silliness, slackness, slenderness,
   slightness, sloth, slothfulness, slouch, slowness, sluggardy,
   sluggishness, stagnancy, stagnation, standpattism, stasis,
   superficiality, tentativeness, torpor, triflingness, triteness,
   triviality, trivialness, unemployment, vacuity, vanity, vapidity,
   vegetation, vita contemplativa, waiting game,
   watching and waiting



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

IDLENESS. The refusal or neglect to engage in any lawful employment, in
order to gain a livelihood.
     2. The vagrant act of 17 G. II. c. 5, which, with some modifications,
has been adopted, in perhaps most of the states, describes idle persons to
be those who, not having wherewith to maintain themselves, live idle,
without employment, and refuse to work for the usual and common, wages.
These are punishable according to the different police regulations, with
fine and imprisonment. In Pennsylvania, vagrancy is punished, on a
conviction before a magistrate, with imprisonment for one mouth.



The Devil's Dictionary (1881-1906):

IDLENESS, n.  A model farm where the devil experiments with seeds of
new sins and promotes the growth of staple vices.