A form of communication which is nothing more than empty boasting. A form of communication in which a person lies in an attempt to make themselves look better.
A person so full of shit, they must flush the toilet 4 times in order to empty the filled bowl.
In all actuality, the term comes from Poker players who would bluff a high stakes pot with a 4 card flush, instead of the true 5 card flush.
I was four flushing you Jack, now let's see your hand...ahh 3 kings, too bad!!