To advance with stealth, unnoticed (literally or figuratively).(verb)
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Use "creep up" in a sentence
"‘Or are you going to try and dismiss that as a bad dream, too?’ he goaded silkily, his eyes riveted to her upturned face as he watched the wild flush creep up to her hairline."
"The slow salt tides of the Atlantic come flooding in over the Manto bank, across the bar of Saltes, and, dividing at the tongue of land that separates the two rivers, creep up the mud banks of the Tinto and the Odiel until they lie deep beside the wharves of Huelva and Palos; but although Huelva still has a trade the tides bring nothing to Palos, and take nothing away with them again."
"Morillo drew on his cigar and Sharpe felt a chill creep up his spine."