1. To begin or commence (something). It's time to lift the curtain on this new project, everyone, so let's not waste any time! After a few delays, the construction crew was finally ready to lift the curtain.

2. To make (something) publicly known; to reveal or disclose the details or truth (about something). In an attempt to head off a public relations disaster regarding his drug use as a college student, the governor decided to lift the curtain at a press conference. I think we had better lift the curtain on our privacy policy if we want consumers to feel secure buying our software.