WordWeb Online

1. Having no limits in range or scope
   "the limitless reaches of outer space";
   - unlimited
    
2. Without limits in extent, size or quantity
   "limitless vastness of our solar system";
   - illimitable, measureless, unmeasured
    
3. Seemingly with no bound in amount, number, degree, or extent
   "a limitless supply of money";
   - boundless, unbounded

See also: bottomless, immeasurable, immensurable, immensurate, infinite, oceanic, unmeasurable, untrammeled [US], untrammelled [Brit, Cdn]

Encyclopedia: Limitless