Unmovable means impossible to move or shift from a position. A massive boulder wedged in a canyon might be unmovable without heavy machinery. An old oak tree with roots spreading deep into the earth stands unmovable against wind and weather.

The word can also describe someone whose mind or decision cannot be changed. When your friend refuses to watch a certain movie no matter what arguments you make, she's being unmovable in her opinion. A judge who remains unmovable in applying the law fairly treats every case by the same standards, regardless of outside pressure.

Sometimes unmovable describes something that feels permanent or fixed, like an unmovable deadline or an unmovable holiday. The Fourth of July is unmovable: it always falls on July 4th, never shifting to a more convenient date.

Note that immovable is more common and means exactly the same thing. Both words work, though you'll see immovable more often in books and formal writing.