noun
sarcasm
SAR-kaz-uhm/ˈsɑːrkæzəm/
Irony used to mock or express contempt.
Her exaggerated praise for the collapsed cake conveys sarcasm.

Etymology
Greek sarkasmos meant a sneer or taunt, from a verb meaning literally “to strip off the flesh.” This image of biting speech underlies sarcasm’s cutting mockery.
In context
British humor leans heavily on sarcasm, understatement, and irony. People say the opposite of what they mean with a completely straight face.