To stiff someone means to not give them something that was promised, especially not giving someone money that was owed.
Stiffed has a bad feeling. It can make people feel angry or cheated.
Examples:
He stiffed me on the bill.
She stiffed him out of his share.
The boss stiffed us on our pay.
I asked for my money, but he stiffed me!
He stiffed me out of a million dollars!
She stiffed me and I was very sad.