Synonyms for (adjective) vast

immense, huge, Brobdingnagian, vast

unusually great in size or amount or degree or especially extent or scope

huge government spending; huge country estates; huge popular demand for higher education; a huge wave; the Los Angeles aqueduct winds like an immense snake along the base of the mountains; immense numbers of birds; at vast (or immense) expense; the vast reaches of outer space; the vast accumulation of knowledge...which we call civilization- W.R.Inge

LESS SPECIFIC: large, big