Source : Webster's Revised Unabridged Dictionary (1913)

Inane \In*ane"\, a. [L. inanis.]
   Without contents; empty; void of sense or intelligence;
   purposeless; pointless; characterless; useless. ``Vague and
   inane instincts.'' --I. Taylor. -- {In*ane"ly}, adv.

Inane \In*ane"\, n.
   That which is void or empty. [R.]

         The undistinguishable inane of infinite space. --Locke.

Source : WordNet®

inane
     adj : complacently or inanely foolish [syn: {asinine}, {fatuous},
           {mindless}, {vacuous}]