Definition of "treacherously" []

• In a treacherous manner. (adverb)

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• "After dominating the recent Chinese Grand Prix, a race run in treacherously wet conditions, Red Bull designer Adrian Newey was asked by Autosport's Edd Straw to explain why his car is so quick in the wet:"
• "In short, it is this great plague of the world, deception, which takes wrong measures, and makes false musters almost in every thing; which sounds a retreat instead of a charge, and a charge instead of a retreat; which overthrows whole armies; and sometimes by one lying word treacherously cast out, turns the fate and fortune of states and empires, and lays the most flourishing monarchies in the dust."
• "Some particular instances of their treachery are here given: There they dealt treacherously, that is, in the places hereafter named [1.]"