I answer no such irrelevant and insidious questions; though were I to answer all that you could put in the course of an hour, you would never be able to prove that it was not Thornton Lacey—for such it certainly was.
Mr. Crawford was no longer the Mr. Crawford who, as the clandestine, insidious, treacherous admirer of Maria Bertram, had been her abhorrence, whom she had hated to see or to speak to, in whom she could believe no good quality to exist, and whose power, even of being agreeable, she had barely acknowledged.
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The debt grew insidiously—just a little at a time and always for a good purpose.
Alan Greenspan -- The Age of Turbulence
We’ve grown accustomed to spending more than we earn, but the increasing debt is an insidious problem.