Definition of "a great deal" 
- (adverb) Very much; to a great extent; a lot; lots.
- (noun) A large amount; a lot.
Use "a great deal" in a sentence
- "CURTIS PELTIER'S CONFESSION not only explained a great deal about Jack Mercier's actions; it also made things a whole lot more difficult for me."
- "One area in which a great deal of research has been done in autoimmune-disease patients is that of probiotic supplementation."
- "Lead, a well-documented neurotoxin, is not a substance that scientists have studied a great deal as a trigger of autoimmune disease, or autogen."