Response to an unfathomable action statement made by another person. The respondent simply and sternly explains this will not take place. Ex: son is not allowed somewhere, but tells his parents, "I'm going anyways!" The parents may respond with, "like hell you are!" Respondent may feel the person had a lot of 'nerve' to say such a thing.
Lover tells their partner during an anniversary they are going to a club instead of spending it with them. Their partner would respond "like hell you are!" Meaning you aren't going, period.
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.