Inexhaustible means impossible to use up or wear out completely. An inexhaustible supply of something never runs out, no matter how much you take from it.

Think of a skilled storyteller with an inexhaustible imagination: they can create story after story, character after character, never running dry of ideas. Or consider a friend with inexhaustible energy who's still ready to play when everyone else needs a rest. The amount of water in Earth's oceans is sometimes described as inexhaustible because it is so vast.

When you exhaust something, you drain it entirely, like exhausting your patience with a difficult puzzle or exhausting the hot water during a long shower. Something inexhaustible can't be exhausted.

Scientists search for inexhaustible energy sources like solar and wind power because, unlike coal or oil, sunlight and wind won't run out. A teacher might admire a student's inexhaustible curiosity, the kind that leads to question after question, always wanting to learn more. The word suggests abundance so great it seems limitless, a supply that keeps giving no matter how much you draw from it.