The Collaborative International Dictionary of English v.0.48:

Dominate \Dom"i*nate\, v. t. [imp. & p. p. Dominated; p. pr. &
   vb. n. Dominating.] [L. dominatus, p. p. of dominari to
   dominate, fr. dominus master, lord. See Dame, and cf.
   Domineer.]
   To predominate over; to rule; to govern. "A city dominated by
   the ax." --Dickens.
   [1913 Webster]

         We everywhere meet with Slavonian nations either
         dominant or dominated.                   --W. Tooke.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dominate \Dom"i*nate\, v. i.
   To be dominant. --Hallam.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dominate
    v 1: be larger in number, quantity, power, status or importance;
         "Money reigns supreme here"; "Hispanics predominate in this
         neighborhood" [syn: predominate, dominate, rule,
         reign, prevail]
    2: be in control; "Her husband completely dominates her"
    3: have dominance or the power to defeat over; "Her pain
       completely mastered her"; "The methods can master the
       problems" [syn: dominate, master]
    4: be greater in significance than; "the tragedy overshadowed
       the couple's happiness" [syn: overshadow, dominate,
       eclipse]
    5: look down on; "The villa dominates the town" [syn:
       dominate, command, overlook, overtop]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "dominate":
   be in, be in force, be the rage, be the rule, be the thing,
   bestraddle, bestride, carry authority, clear, command, control,
   crack the whip, deprive of freedom, dictate, direct,
   disenfranchise, disfranchise, domineer, enslave, enthrall, govern,
   handle, have clout, have power, have the ascendancy,
   have the power, have the right, have the say, hold captive,
   hold down, hold in bondage, hold in captivity, hold in leash,
   hold in subjection, hypnotize, keep down, keep under, lead,
   lead captive, look down upon, make dependent, manage, master,
   mesmerize, obtain, outtop, overarch, overlook, overshadow, overtop,
   peonize, play first fiddle, possess authority, predominate,
   preponderate, prevail, reign, rise above, rule, rule the roost,
   subject, subjugate, subordinate, supervise, surmount, take captive,
   take the lead, top, tower above, tower over, twist, vassalize,
   wear the pants, wield authority