1. Greater in size, amount, or degree: Howard stood on the tourist lookout of the mountain and admired the vast valley and river system he could see below him.
2. Very extensive in degree or intensity: Hannah experienced a vast relief when she learned that her cat was not seriously ill.

Sharon has a vast amount of knowledge on the etymologies, or origins, of words.

The written assignment for his chemistry course required a vaster amount of research than Harrison had anticipated and so he had to study all night to complete the assignment on time.

3. Etymology: from Middle French vaste, from Latin vastus, "immense, extensive, huge"; also, "desolate, unoccupied, empty".

Latin vastus (short "a") is said to have been distinct from vastus (long "a", [VAYS tuhs]), "desolate"; however, the two forms apparently merged early in Latin, so that the English vast is related to "waste", as in Old English weste, "desolate".

The Latin vastus is believed by some scholars to originally have meant "empty, unoccupied, deserted".