facetious
adjective disapproving uk/fəˈsiː.ʃəs/ us/fəˈsiː.ʃəs/
（尤指不问场合）好开玩笑的;滑稽的，诙谐的
not serious about a serious subject, in an attempt to be funny or to appear clever
facetious remarks 不合时宜的发言
He's just being facetious. 他只是在乱开玩笑。
Synonym: tongue-in-cheek