When one moves his hand in a motion that resembles masturbating. This is usually done when another person is speaking to show how uninterested you are in what he or she has to say. Slow jerkin must be done in a slower fashion that most are used to in order to exaggerate how boring or lame the person's story is. When executing this you MUST ALWAYS finish and preferably act out cumming on yourself. Once you get good at this you can try more advanced techniques such as slow jerking the person who is speaking and then making both of yours touch. Also eye contact is crucial in slow jerkin.
Person 1: Hey how's it going?
Person 2: Well not too good actually, my girlfriend doesn't like the same kind of music as me. My apartment doesn't get enough southern light and the rug I just got really clashes with the rest of my furnit... OH DUDE YOUR DOIN IT TOO SLOW THATS NOT HOW YOU DO THAT
Person 1: (Slow Jerkin while maintaining eye contact)