Retard Units is an unofficial synonym for "imperial measurements". As the rest of the world use metrics, the internet culture started mocking the medieval traditions of the Americans, and how little sense the usage of imperials pose compared to metrics.
Space begins 100 kilometers from the earth, that's 62,14 miles in Retard Units.
The T.D. unit is a standard measurement for smell intensity. The acronym was chosen to be T.D. as its not commonly known as anything else. The measure has typical values from 1 to 5, 1 being a mild stink and 5 a ghastly stench. On the odd occasion a 6 can be recorded but this is often associated with asphyxiation, leading ultimatley to death.
Bob: Hey man keep away from that guy his rocking like 5 T.D. units!
Jim: Nah man i can handle it.........holy shit he stinks!!!!!!!!!! I can't breathe!!!!!!!!!!!!!!!!!!!!!!!
Bob: Dude it must be a 6 then, better get you to a hospital.
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.