Boundless, a.
Without bounds or confines; illimitable; vast; unlimited. "The boundless sky." Bryant. "The boundless ocean." Dryden. "Boundless rapacity." "Boundless prospect of gain." Macaulay.
Syn. -- Unlimited; unconfined; immeasurable; illimitable; infinite. -- Bound"less*ly, adv. -- Bound"less*ness, n.
Shades of meaning
Fernald has no entry of its own for boundless; he lists it under infinite.
Where he writes about it:
So, too, boundless, illimitable, limitless, measureless, and unlimited are loosely used in reference to what has no apparent or readily determinable limits in space or time; as, we speak of the boundless ocean. — from infinite