The phrase "global unveiling" refers to the act of revealing something, such as a product or information, on a worldwide scale. It means that the unveiling is happening for everyone around the world to see or learn about.
Nissan has announced global unveiling of the 2018 LEAF with semi-autonomous ProPILOT Park technology on September 6. (auto.economictimes.indiatimes.com)
This comes before the car's official global unveiling at the 2018 Beijing motor show on April 25. (overdrive.in)
A new Nokia tablet has apparently been spotted on GFXBench, which suggests that consumers could see HMD Global unveil the device on Feb. 26 at the MWC 2017. (techtimes.com)