The Hound of the Baskervilles by Sir Arthur Conan Doyle Chapter 1 Mr. Sherlock Holmes Mr. Sherlock Holmes, who was usually very late in the mornings, save upon those not infrequent occasions when he was up all night, was seated at the breakfast table.
There are no more uses of "infrequent" in the book.
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You’d be surprised how infrequently I get something I truly want."
Kiera Cass -- The Elite
Gradually, their visits became shorter and more infrequent.