When something is so disappointing and depressing that you confuse the two.
Your friend: *tips over your beer accidentally*
You: Dude, that was so disapressing...
A combination of disappointing and depressing. When you can't decide quite how bad something is, if it's depressing or just disappointing, call it both... disapressing.
Ryan: Yo volleyball sucked day, it was not fun.
Sean: That shit was disapressing.