The adjective unfettered describes something or someone uninhibited and unrestrained. If you write mysteries novels for a living you probably turn your unfettered imagination to murder and mayhem.
Unfettered comes from the Old English root word fetor, which was a chain or shackle for the feet. Un- means "not," so originally the word literally meant "not chained or shackled." Today there isn't much real shackling going on, so the adjective unfettered mainly describes something that is free or unrestrained. You'll see such uses as unfettered emotions, unfettered stock market growth, and unfettered speech.