(uncountable) The state of being facetious / (countable) The product or result of being facetious.

plural of facetiousness

Treating serious issues with (often deliberately) inappropriate humour; flippant. / Pleasantly humorous; jocular.

In a facetious or flippant manner; in a manner that treats serious issues with deliberately inappropriate humor / (dated) In a pleasantly humorous or playful fashion.

(Caribbean, Jamaica) arrogantly rude; feisty

(rare) facetious behavior