in a deceitful manner; cunningly: They slyly plot to overthrow us.
in a roguish or mischievous way: Some were serious, while others slyly winked at the camera.

Origin of slyly

1350–1400 (def. 1); 1835–40 (def. 2); sly + -ly Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for slyly

Contemporary Examples of slyly

Historical Examples of slyly

Word Origin and History for slyly

c.1200, from sly (adj.) + -ly (2).

Online Etymology Dictionary, © 2010 Douglas Harper