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- not supposed to
not supposed to
(It's) not supposed to.
and (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.