1.
If you describe a plan or idea as ~, you are criticizing it because it is unrealistic and shows a belief that things can be improved much more than is possible.
He was pursuing a ~ dream of world prosperity...
A complete absence of national border controls is as ~ today as the vision of world government.
= idealistic
ADJ disapproval
2.
Utopian is used to describe political or religious philosophies which claim that it is possible to build a new and perfect society in which everyone is happy. (FORMAL)
His was a ~ vision of nature in its purest form.
ADJ: usu ADJ n