What does the JIP in baseball stand for?

IP stands for Innings Pitched. It is a pitching statistics that records the amount of innings the pitcher pitched.

It can be divided into thirds by the outs that were recorded while the pitcher was still on the mound.

For example: Its the 5th inning and there are 2 outs. The pitcher needs to be taken out of the game and is replaced with another pitcher. The number of innings pitched for this game would be 4 2/3. The relief pitcher would then pitch 2 1/3. This would add up to the complete 7 inning game.