1 - Expert systems is commonly used to replace words in a lame come-back to an insult.
2 - It can also be used to confuse a person after they give you a compliment
1- Stupidlittlefucker - "You stupid fag, you just ruined the game, why don't you just fuck off"
Phuzzletoff - "If by fuck off, you mean expert systems, then yes."
2 - Reallyhotchick - "Hey great game! You were really good"
Phuzzletoff - "If by really good, you mean expert systems, then that's disgusting! But I'm in."