An affirmative, used to agree to something, show interest in something, or react to something strange or awkward.
Rebecca: Jon has been such a jerk lately.
Amy: Oh, true.
Joe: I'm about to hit up karaoke with the crew, wanna come?
Matt: Oh, true? I'll see if I can.
Matt: What happened to you yesterday?
Rebecca: Well, I went to Joe's house but when I knocked on the door, his brother answered and said Joe had just left to go get food. I was like, 'Oh, TRUE?' So I stood by my car awkwardly waiting for him to get back for like twenty minutes.
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.
You didn't get any napkins with your takeout pork fried rice? Womp womp.