/əˈblɪɡətɔːri/
ob·liga·tory
BrE /əˈblɪɡətri/
NAmE /əˈblɪɡətɔːri/
~ (for sb) (to do sth)
(formal)
that you must do because of the law, rules, etc.
SYN compulsory
It is obligatory for all employees to wear protective clothing.
OPP optional
(often humorous)
that you do because you always do it, or other people in the same situation always do it
In the mid 60s he took the almost obligatory trip to India.