be duty bound

be duty bound

To be obligated or expected to do something. Now that our parents are dead, I'm duty bound to care for my siblings. As a parent, you are duty bound to protect your child.
See also: bound, duty

be/feel duty/honour ˈbound to do something

(British English) (American English be/feel duty/honor ˈbound to do something) (formal) feel that you must do something because of your sense of moral duty: She felt honour bound to attend as she had promised to.Most people think that children are duty bound to look after their parents when they are old.