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:

Overpowering \O`ver*pow"er*ing\, a.
   Excelling in power; too powerful; irresistible. --
   O`ver*pow"er*ing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overpowering
    adj 1: so strong as to be irresistible; "an overpowering need
           for solitude"; "the temptation to despair may become
           overwhelming"; "an overwhelming majority" [syn:
           overpowering, overwhelming]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "overpowering":
   agitating, breathtaking, charged, cliff-hanging, compelling,
   disquieting, distracting, disturbing, electric, exciting,
   exhilarating, galvanic, heady, heart-expanding, heart-stirring,
   heart-swelling, heart-thrilling, impenetrable, impregnable,
   impressive, incontestable, indomitable, inexpugnable, inflammatory,
   insuperable, intoxicating, invincible, inviolable, invulnerable,
   irresistible, jarring, jolting, maddening, mind-blowing, moving,
   oppressive, overcoming, overmastering, overmatching, overwhelming,
   perturbing, piquant, powerful, provocative, provoking, ravishing,
   resistless, soul-stirring, spirit-stirring, stimulating,
   stimulative, stirring, striking, suspenseful, suspensive,
   tantalizing, telling, thrilling, thrilly, troubling, unassailable,
   unbearable, unbeatable, unconquerable, unendurable, unsettling,
   unsubduable, unsurmountable, unyielding, upsetting