Definitions

1. verb

to become or make (someone) less accustomed to something

“The change in climate has unaccustomed many people to extreme weather conditions.”

2. verb (archaic)

to accustom, to make (someone) accustomed to something

“It was unaccustomed to such lavish feasts, so it felt out of place.”

3. noun

the act of becoming or making someone less accustomed to something

“The process of unaccustoming the team to their old playing style proved to be challenging.”