In a way that is not courteous. Impolitely(adverb)
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Use "uncourteously" in a sentence
"“I must have mistaken the person to whom the letter was addressed, then;” and, as she spoke, Mistress Martha Trapbois was in the act of stooping to lift the paper which had been so uncourteously received."
"It struck me as being almost uncourteously decided."
"I did full uncourteously unto Sir Launcelot, and full unknightly, and full knightly and courteously he did to me again; for an he had been as ungentle to me as I was to him, this day I had won no worship."