Supertruth is the amalgamation of two unrelated stories (one of which MUST be true) in order to create a single new story. This is NOT a lie, it is the supertruth.
The supertruth is basically a hyper-exaggerated version of actual events from multiple (2 or more) sources.
I made a slice of toast. -> this is the truth
I created a wireless mouse for my computer -> this is the supertruth, because I took the fact that I actually made myself toast, and I mixed it in with an episode of MacGyver where MacGyver made something far more awesome than toast.