wat means "What About Today" and it is used to ask if someone can go out with you
dude: Hey sir, WAT?
sir: Idk I'm busy with home
dude: If you say so
Wat basically means and sounds exactly as what does. Because wat IS what.
R1: 'Wat up man!
R2: 'Wat?'
R3: 'He said Wat up man!
A word used by intellectual's meaning what
John said what
Me an intellectual: WAT