Source : Webster's Revised Unabridged Dictionary (1913)

Obtrusive \Ob*tru"sive\, a.
   Disposed to obtrude; inclined to intrude or thrust one's self
   or one's opinions upon others, or to enter uninvited;
   forward; pushing; intrusive. -- {Ob*tru"sive*ly}, adv. --
   {Ob*tru"sive*ness}, n.

         Not obvious, not obtrusive, but retired. --Milton.

Source : WordNet®

obtrusiveness
     n : an unwelcome conspicuousness [ant: {unobtrusiveness}]