Wiktionary
n. (context idiomatic English) A large number or amount.
WordNet
n. (often followed by `of') a large number or amount or extent; "a batch of letters"; "a deal of trouble"; "a lot of money"; "he made a mint on the stock market"; "it must have cost plenty" [syn: batch, deal, flock, good deal, hatful, heap, lot, mass, mess, mickle, mint, muckle, peck, pile, plenty, pot, quite a little, raft, sight, slew, spate, stack, tidy sum, wad, whole lot, whole slew]
Usage examples of "great deal".
Early in 1862 David was appointed collector of customs at San Francisco, and during the time he held that office he had a great deal to say about federal patronage within the state.
I have, as you are aware, thought a great deal about the relation of this war to slavery and you all must remember that several weeks ago, I read to you an order I had prepared on this subject.
Formalities, as Lincoln confided to Tad, take a great deal of time and patience.