The Collaborative International Dictionary of English v.0.48:

Meaning \Mean"ing\, n.
   1. That which is meant or intended; intent; purpose; aim;
      object; as, a mischievous meaning was apparent.
      [1913 Webster]

            If there be any good meaning towards you. --Shak.
      [1913 Webster]

   2. That which is signified, whether by act lanquage;
      signification; sense; import; as, the meaning of a hint.
      [1913 Webster]

   3. Sense; power of thinking. [R.]
      [1913 Webster] -- Mean"ing*less, a. -- Mean"ing*ly,
      adv.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

meaningless \meaningless\ adj.
   having no meaning; of no value; as, a meaningless endeavor; a
   meaningless life; a meaningless explanation. Opposite of
   meaningful. [Narrower terms: insignificant ; {mindless,
   unmeaning ; {nonsense(prenominal), nonsensical ; {pointless,
   purposeless ] Also See: {insignificant, unimportant,
   purposeless, unimportant.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

meaningless
    adj 1: having no meaning or direction or purpose; "a meaningless
           endeavor"; "a meaningless life"; "a verbose but
           meaningless explanation" [syn: meaningless,
           nonmeaningful] [ant: meaningful]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "meaningless":
   absurd, aimless, amorphous, asinine, blank, bootless, capricious,
   casual, designless, desultory, disarticulated, discontinuous,
   disinclined to communicate, disjunct, disordered, dispersed,
   disproportionate, empty, erratic, fatuous, feckless, fitful,
   foolish, formless, frivolous, fustian, garbled, good-for-nothing,
   gratuitous, haphazard, hit-or-miss, hollow, immethodical,
   importless, impotent, inane, inchoate, incoherent, inconsequential,
   indiscriminate, ineffective, ineffectual, inefficacious,
   insignificant, insubstantial, irregular, irrelevant, misshapen,
   no go, nonconnotative, nondenotative, nonsensical, nonsymmetrical,
   nonsystematic, nonuniform, nugatory, null, of no use, orderless,
   paltry, phatic, planless, pointless, preposterous, promiscuous,
   puny, purportless, purposeless, random, ridiculous, scrambled,
   secretive, senseless, shapeless, silly, spasmodic, sporadic,
   straggling, straggly, superfluous, systemless, trifling, trivial,
   unarranged, unavailing, unclassified, uncommunicative,
   unconversable, undirected, ungraded, unimportant, unjoined,
   unmeaning, unmethodical, unordered, unorganized, unpurposed,
   unsignificant, unsociable, unsorted, unsubstantial, unsymmetrical,
   unsystematic, ununiform, useless, vacant, vacuous, vague, vain,
   valueless, wandering, worthless