The full range of possibilities; everything. Used with the.
(UK, colloquial) All inclusive; everything; a whole package.
I thought he was only going to buy the basic kit, but he bought the full monty.
Origin of full-monty
Unknown. First appeared in print in 1980s, but probably existed before that. The most common theory for its origin is that a purchase (especially that of a full three-piece suit) from Montague Maurice Burton (1885-1952), founder of Burton Menswear, was known as a "full Monty". According to the OED, this etymology is "perhaps the most plausible".