Knavishly

1. (adv.) In a knavish manner; dishonestly; fraudulently.

2. (adv.) Mischievously; waggishly; roguishly.

Thesaurus Entries

as a joke, devilishly, elfishly, for amusement, for fun, for kicks, for laughs, for sport, impishly, in jest, in joke, in play, in sport, jestingly, jokingly, knavishly, mischievously, playfully, prankishly, puckishly, roguishly, scampishly, sportively, waggishly