Get the boot means to be forced out. In modern English, it often refers to losing a job, being told to leave a place, or having an idea rejected.
The phrase is widely understood as coming from the image of someone being sent away with a kick from a boot. Even when no actual kick is involved, the expression keeps that sense of sudden, rough dismissal.
Today, people use it in both serious and informal situations. It can describe what happens to a person, but also to a plan, application, or suggestion.
- He got the boot after arriving late for the fifth time.
- Our original marketing plan got the boot when the budget changed.
- If you keep breaking the rules, you might get the boot from the club.
This idiom is casual, so it fits conversation and informal writing better than formal business language. In formal contexts, people usually say was fired, was removed, or was rejected instead.