One whose imagination overpowers his reason and controls his judgment; an unpractical schemer; one who builds castles in the air; a daydreamer
If you refer to someone as a visionary, you mean that they have strong, original ideas about how things might be different in the future, especially about how things might be improved. An entrepreneur is more than just a risk taker. He is a visionary
a person given to fanciful speculations and enthusiasms with little regard for what is actually possible
Affected by phantoms; disposed to receive impressions on the imagination; given to reverie; apt to receive, and act upon, fancies as if they were realities