I quite often hear people say “push off” to mean “go / leave“. See this example:

• We’re going to push off at 2pm tomorrow.

I’ve checked the Cambridge Dictionary (UK) and Dictionary.com (US), and discovered that “push off” means “depart“  or “leave“ in the U.S. dictionary, while the U.K. dictionary doesn’t include this meaning. See how we mix English varieties when we speak and write? The gap between UK English and US English is getting narrower. One fine day, there won’t be a gap anymore, and we would use both varieties interchangeably without having the need to distinguish which is UK English and which is US English.