Source : Webster's Revised Unabridged Dictionary (1913)

Inanity \In*an"i*ty\, n.; pl. {Inanities}. [L. inanitas, fr.
   inanis empty: cf. F. inanit['e]. See {Inane}.]
   1. Inanition; void space; vacuity; emptiness.

   2. Want of seriousness; aimlessness; frivolity.

   3. An inane, useless thing or pursuit; a vanity; a silly
      object; -- chiefly in pl.; as, the inanities of the world.

Source : WordNet®

inanity
     n : total lack of meaning or ideas [syn: {senselessness}, {mindlessness},
          {vacuity}, {pointlessness}]