Quite simply, the meaning of life.
Mesty originally derives from ancient scholars in Greece and Rome from the original Latin word 'Mestis'- 'mes' the Latin word for 'meaning', and 'tis' meaning 'existence' or 'life' in English. The word in modern times has been forgotten and left behind and only used by those experienced in rock music, drugs and the secret third step only known to the inner members of the Mesty Clan.
Andy: Oi Tristan.
Tristan: Dude, are you trippin'?
Andy: Yeah man.