Electronic – What does +9/7.2V mean

Some schematic programs use this as a symbol to show that the pin is specifically not connected to anything.

However, this looks to be a schematic from Eagle. Eagle requires no such symbol. Output or passive pins are allowed to not be connected without any electrical rules check error. You can make a symbol and footprint for anything you want in Eagle, so only the designer knows for sure what this means. It could mean a test point, but most likely not since there is no component designator. A bunch of test points on the board are pretty useless unless labeled, so I don't think that's it. Most likely whoever created that schematic was used to a different schematic program and felt compelled to put Xs there to indicate not connected. In Eagle, you simply don't connect anything and don't give it a name and it won't be connected anywhere.

This device is a transient voltage suppressor for USB D+ and D- signals. It protects the device from static voltages that may develop when inserting or removing USB devices to connectors.

The four diodes (on side) act as clamping diodes that conduct to suppress ESD.

This or similar device can be found in this Semtech catalog