Definition of "connoisseur"

It is evident, in spite of his frequent attention to her while she draws, that in fact he knows nothing of the matter. He admires as a lover, not as a connoisseur.

1811, [Jane Austen], chapter III, in Sense and Sensibility […], volume I, London: […] C[harles] Roworth, […], and published by T[homas] Egerton, […]

No; nonsense, Naumann! English ladies are not at everybody’s service as models. And you want to express too much with your painting. You would only have made a better or worse portrait with a background which every connoisseur would give a different reason for or against.

1871–1872, George Eliot [pseudonym; Mary Ann Evans], chapter XIX, in Middlemarch […], volumes (please specify |volume=I to IV), Edinburgh, London: William Blackwood and Sons, book (please specify |book=I to VIII)

This, when it was brought to him, he drank slowly, like a connoisseur, lingering on the taste and still looking about him at the cliffs and up at our signboard.

1881–1882, Robert Louis Stevenson, Treasure Island, London, Paris: Cassell & Company, published 14 November 1883

Real connoisseurs know that to nose and taste properly you have to add still water to your tulip-shaped glass so that the alcohol doesn't overwhelm you.

2002 October 20, Bob Morris, “The Age of Dissonance”, in The New York Times‎