Facetious (adj.): Flippant, especially when it comes to very serious issues
One who is facetious may be playing games on his phone when his doctor is informing him that he has a serious health condition. Or perhaps one’s father was in a serious car accident late one afternoon– and the facetious family member decided to go to a birthday party that night instead of visiting her father. Facetious individuals do not take situations seriously or appropriately and are flippant. One wonderful synonym for facetious is sardonic.