the intentional slurring together of the Englishwordsforget + about + it toward the effect of expressing surety, wonder or degree of approval; the usage is largely associated with New York soldiers of the mafia.
The physical space where you forgot why you left one room to go to another room to get whatever it was you wanted, sometimes forcing you to go back to the first room. Maybe several times.
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.