Source : Webster's Revised Unabridged Dictionary (1913)

Self-important \Self`-im*por"tant\, a.
   Having or manifesting an exaggerated idea of one's own
   importance or merit.

Source : WordNet®

self-important
     adj : having or showing feelings of unwarranted importance out of
           overbearing pride; "an arrogant official"; "arrogant
           claims"; "chesty as a peacock" [syn: {arrogant}, {chesty}]