In a lecherous manner, in the way of a lecher.(adverb)
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Use "lecherously" in a sentence
"I fall into the same mind-frame, thinking lecherously, I want it all."
"“Sixty-five,” another man proposed, smiling lecherously, his tongue flicking out and licking his lips."
"Ten days was enough of it, though, for she was an avid little beast who preferred quantity to quality-unlike Elspeth, for example, whose beguiling innocence masked the most lecherously inventive mind of the last century, and whose conduct on our honeymoon would have caused the good citizens of nearby Troon to burn her at the stake, if they'd known."