1. Intended, expected, or believed to do something. This new software is supposed to make things a lot more efficient, but I find it so confusing that everything is taking me twice as long! We're supposed to arrive around 3 PM, assuming our flights aren't delayed.
2. Required or obligated to do something. I was supposed to be home an hour ago—my parents are going to kill me! Please don't distract him, he's supposed to be cleaning his room.
3. Allowed or permitted to do something. (Chiefly used in questions and negative constructions.) You're not supposed to go in there! Are you sure you're supposed to be in here?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
(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.
supposed toand someone or something is supposed to
Someone or something is meant to do something. (Frequently, in speech, supposed is reduced to s'posed. The words someone or something can be replaced with nouns or pronouns, or used themselves.) Mary: They didn't deliver the flowers we ordered. Sue: Supposed to. Give them a call. Sally: This screw doesn't fit into hole number seven in the way the instructions say it should. Bill: It's supposed to. Something's wrong.
supposed to do something
expected or intended to do something; obliged or allowed to do something. You're supposed to say "excuse me" when you burp. Mom says you're supposed to come inside for dinner now.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
1. Intended to; also, believed to, expected to. For example, This pill is supposed to relieve your pain, or You're supposed to be my partner. [Early 1300s]
2. Required to, as in He is supposed to call home. [Mid-1800s]
3. not supposed to. Not permitted to, as in You're not supposed to smoke in here.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.