The Collaborative International Dictionary of English v.0.48:

Overpower \O`ver*pow"er\, v. t. [imp. & p. p. Overpowered; p.
   pr. & vb. n. Overpowering.]
   To excel or exceed in power; to cause to yield by superior
   power; to vanquish; to subdue; as, the light overpowers the
   eyes. "And overpower'd that gallant few." --Wordsworth.
   [1913 Webster]

   Syn: To overbear; overcome; vanquish; defeat; crush;
        overwhelm; overthrow; rout; conquer; subdue.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

overpowered \overpowered\ adj.
   1. rendered powerless especially by an excessive amount or
      profusion of something.

   Syn: overcome, overwhelmed, swamped, engulfed.
        [WordNet 1.5]

   2. Having more than the required power; as, an overpowered
      hot rod. [Colloq.]
      [PJC]