1. (superl.) Waste; desert; desolate; lonely.

2. (superl.) of the vast ocean; vast mountains; the vast empire of Russia.

3. (superl.) Very great in numbers, quantity, or amount; as, a vast army; a vast sum of money.

4. (superl.) Very great in importance; as, a subject of vast concern.

5. (n.) A waste region; boundless space; immensity.