Definition of "first water" [first water]

• The highest degree of quality or purity in diamonds or pearls. (noun)
• The foremost rank or quality: a pianist of the first water. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Le Fever’s son to you; — a tear of joy of the first water sparkled in my uncle Toby’s eye, and another, the fellow to it, in the corporal’s, as the proposition was made; — you will see why when you read Le Fever’s story: — fool that"