adv. [f. prec. + -LY2.] In a treacherous manner; by or with treachery.

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a. 1340.  Hampole, Psalter, xiii. 5. With þaire tongis tricherously þai wroght.

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1596.  Spenser, F. Q., V. vi. 26. A Spaniell wayting carefully Least any should betray his Lady treacherously.

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1678.  Wanley, Wond. Lit. World, V. ii. § 6. 469/1. Gratian … was treacherously murdered.

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1740.  Ipswich Jrnl., 5 Jan., 1/3. Kouli Kan caus’d the Great Mogul to be arrested with all his Retinue, and immediately after sent 20,000 Men, who treacherously made themselves Master of Deli the Capital of the Kingdom.

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1860.  Tyndall, Glac., I. xi. 69. I stepped … upon a block of granite…; it treacherously turned under me.

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