Unbelievable, incredible, fantastic; usually refers to some extremely excellent food or something to be appreciated or incredible thing. Also can relate to unreal good sex, your partner, the act, or yourself. Can be applied to many different things that can be appreciated or found to be unbelievable.
The delicious dinner that you madelast night was unfuckingreal, but when we got into bed later and we had such great sex, it was really unfuckingreal.
A term created by Rea Garvey (Irish sing-songwriter) as one of the coaches during the Voice of Germany (2012). "Unfassbar" is the German definition of unbelievable or unconceivable. He uses this term when he is breathtaken, speechless and in awe of a singer's performance. An english translation would be something along the lines of "unfuckingbelievable".
Wow - your voice is "unfuckingfassbar", meaning it is incredibly good - it blew me away.