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

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

Encyclopedia: Limitless