I'm not seeing anyone put a definition to Jedi Huffing so I'll give it a try.
Jedi Huffing - The act of extracting high value gas from a J-Space site with enemy NPCs on grid. To put it briefly, the Prospect and in some cases the Venture are capable of avoiding the NPCs that normally force miners to leave until destroyed by combat craft. The idea is you are "at peace" with them like a Jedi, but it is simply speedtanking the NPCs so that you may harvest freely.
J-Space - Another name for star systems accessible only by wormholes. Each of these system's name begins with the letter "J" followed by a series of numbers, hence the moniker "J-Space"
Speedtanking - Otherwise known as "Sig Tanking" or "Signature Tanking", it is a method of avoiding incoming enemy fire with a combination of high speed, low signature radius, and high transversal/angular velocity from the enemy ships.