Source : Webster's Revised Unabridged Dictionary (1913)

Opener \O"pen*er\, n.
   One who, or that which, opens. ``True opener of my eyes.''
   --Milton.

Source : WordNet®

opener
     n 1: the first event in a series; "she played Chopin for her
          opener"; "the season's opener was a game agains the
          Yankees"
     2: a person who unfastens or unwraps or opens; "children are
        talented undoers of their shoelaces" [syn: {undoer}, {unfastener},
         {untier}]
     3: a hand tool used for opening sealed containers (bottles or
        cans)