Originally the
past tense of "to shit," but shat has evolved into
something more. Shat doesn't share the harsh connotations of "shit," nor does it share it's seriousness.
Shat can be used in multiple fashions, such as "shatty," "shatting," "shatness," and even "shatmaster." It's uses are ambiguous, so even more exotic fashions of use are still evolving.