Boundless means having no limit at all. Nothing anybody could reach the end of.
It attaches to qualities rather than to physical things, so boundless energy, boundless enthusiasm and boundless optimism are all standard, and each is a compliment. Landscape borrows it for effect, and a boundless plain stretches past the horizon. The word is a straightforward compound of bound, meaning a limit, and -less. Limitless and infinite are its close relatives, and infinite belongs more to mathematics.
1adjectiveboundlessHaving no limit or end.
“He had boundless enthusiasm for the project.”
Old English
bund-
Middle English
bound
English
bound
English, today
boundless
From bound + -less. bound comes from Middle English bound, bund and bounden, bunden, ibunden, ȝebunden, from Old English bund- and bunden, ġebunden respectively. See bind.
Etymology from Wiktionary, CC BY-SA