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Phrase(s): a big drink of water [and] a tall drink of water
1. Fig. a very tall person. • Tim is sure a big drink of water. • Kelly grew into a tall drink of water. 2. Fig. a boring person or thing. (A pun on "hard to take.") • She is a big drink of water, but she could be worse. • The lecture was a big drink of water.
McGrawhill's American Idioms And Phrasal Verbs