Source : Webster's Revised Unabridged Dictionary (1913)

Powerful \Pow"er*ful\, a.
   1. Full of power; capable of producing great effects of any
      kind; potent; mighty; efficacious; intense; as, a powerful
      man or beast; a powerful engine; a powerful argument; a
      powerful light; a powerful vessel.

            The powerful grace that lies In herbs, plants,
            stones, and their true qualities.     --Shak.

   2. (Mining) Large; capacious; -- said of veins of ore.

   Syn: Mighty; strong; potent; forcible; efficacious;
        energetic; intense. -- {Pow"er*ful*ly}, adv. --
        {Pow"er*ful*ness}, n.

Source : WordNet®

powerfully
     adv 1: in a powerful manner; "the federal government replaced the
            powerfully pro-settler Sir Godfrey Huggins with the
            even tougher and more determined ex-trade unionist"
            [syn: {strongly}]
     2: in a manner having a powerful influence; "Clytemnestra's
        ghost crying in the night for vengeance remained most
        potently in the audience's mind" [syn: {potently}]