(SOMEONE'S) NOT SUPPOSED TO.
(Someone's) not supposed to.: translation
(It's) not supposed to. & (Someone's) not supposed to.
a phrase indicating that someone or something is not meant to do something. (Often with a person's name or a pronoun as a subject. See the examples.) •
Fred: This little piece keeps falling off. Clerk: It's not supposed to.
•
Bill: Tom just called from Detroit and says he's coming back tomorrow. Mary: That's funny. He's not supposed to.