Idioms
be supposed to do/be something
1 to be expected or required to do/be something according to a rule, a custom, an arrangement, etc You're supposed to buy a ticket, but not many people do.
I thought we were supposed to be paid today.
The engine doesn't sound like it's supposed to.
You were supposed to be here an hour ago!
How was I supposed to know you were waiting for me?
‘Yes and no.’ ‘What is that supposed to mean?’ (= showing that you are annoyed)
+ EXPRESS YOURSELF
2 to be generally believed or expected to be/do something I haven't seen it myself, but it's supposed to be a great movie.
She's supposed to have had hundreds of lovers.
not be supposed to do something
to not be allowed to do something You're not supposed to walk on the grass.
Oxford Advanced Learner's Dictionary 9th edition © Oxford University Press, 2015
supposed
sup·posed [supposed] [səˈpəʊzd] [səˈpoʊzd] adjective only before noun
used to show that you think that a claim, statement or way of describing sb/sth is not true or correct, although it is generally believed to be
Syn: alleged
• This is the opinion of the supposed experts.
• When did this supposed accident happen?