There's a jab that you don't turn over, it just goes with the palm ending facing sideways. You can't get power on it but it's used to get through the middle of the guard.
http://www.expertboxing.com/boxing-training/punching-techniques/44-the-ultimate-boxing-jab-guide Cheers mate
a jab is any shot from the lead/front hand that travels in a linear motion. all the joints work to keep fist traveling in a straight line from A to B. there are so many variations and so many interpretations and names you can call different movements. this is what i have found to be the commonality of the jab. i have my athlete drill a lot of Boxer A has Jab and Boxer B has lead hook. i use this drill to teach positioning for a boxer to keep away from a pressure fighter and a fighter to get inside a boxer. i had to come up with a definition of a jab because they're both using their lead hand and i wanted them to have the opportunity to "invent" ways of creating space or taking space away. i define a hook as any punch that is a rotational motion, which means that at least one joint needs to be "locked" in position (like the elbow) and at leat one other joint is going to be a pivot (the rear hip, or shoulder, etc).
