Booming Blade says the following:

If the target willingly moves 5 feet or more before (the start of your next turn), the target takes 1d8 thunder damage, and the spell ends.

Is “willingly” an actual game term? Or is it just meant to be taken for the obvious meaning, that being compelled to move magically, or being shoved doesn’t count?

What are some other examples of “Willingly” being used in D&D?