Source : Webster's Revised Unabridged Dictionary (1913)

Overzealous \O"ver*zeal"ous\, a.
   Too zealous.

Source : WordNet®

overzealous
     adj : marked by excessive enthusiasm for and intense devotion to a
           cause or idea; "rabid isolationist" [syn: {fanatic}, {fanatical},
            {rabid}]