1) Too great, too wonderful to be expressed or described in mere words. An indescribable feeling, person or thing that exists only in fleeting thoughts.
2) A term used by an angel to describe the Plan of God; Her Ineffable Plan. Separate from the Great Plan.
Anything ineffable is unspeakably beautiful, moving, or horrible. It's beyond expression. If something is so powerful or emotional that you can't even describe it, it's ineffable. Ineffable ideas and emotions are difficult to put into words.
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.