Fugacity

(Noun) A typical word your engineering professor will yell at you in the middle of lecture to flex how he is smarter than you but never explains what it is.

Student: "Dr. Peng, I was wondering how you solve this carnot cycle?"
Smartass Asian Professor: "Fugacity"
Student: "I don't understand what you mean"
Smartass Asian Professor: "I can't help you. Go work at McDonald's or quit school. This is highschool level problem."