Something that is inflexible cannot be altered in any way, even if the situation changes.
Workers insisted the new system was too inflexible.
工人们坚持认为新制度过于僵化。
If you say that someone is inflexible, you are criticizing them because they refuse to change their mind or alter their way of doing things.
His opponents viewed him as stubborn, dogmatic, and inflexible.
他的对手认为他固执、教条而且死板。