Source : Webster's Revised Unabridged Dictionary (1913)

Inadvertent \In`ad*vert"ent\, a. [Cf. F. inadvertant. See 2d
   {In-}, and {Advert}.]
   Not turning the mind to a matter; heedless; careless;
   negligent; inattentive.

         An inadvertent step may crush the snail That crawls at
         evening in the public path.              --Cowper.
   -- {In`ad*vert"ent*ly}, adv.

Source : WordNet®

inadvertent
     adj : without intention (especially resulting from heedless
           action); "with an inadvertent gesture she swept the
           vase off the table"; "accidental poisoning"; "an
           accidental shooting" [syn: {accidental}]