InsidIously, adv

[Eng. insidious; -ly. In an insidious manner, treacherously, craftily, slyly. "No soft and costly sofa there Insidiously stretched out its lazy length." Words worth: Excursion , bk. vii. In-sid-I-ous-ne , s. [Eng. insidious; -ne .] The quality or state of being insidious; deceitfulne , treachery. "None of its lurking insidiousne , of its surprising violence, of its rancorous venom."-Barrow: Sermons.