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straighten someone or something up
1. to put someone or something into an upright position. The fence is tilted. Please straighten that post up when you get a chance. Bill, you're slouching again. Straighten up your back.
2. to tidy up someone or something. John straightened himself up a little before going out for dinner. This room is a mess. Let's straighten up this place, right now!
1. to sit or stand more straight. Billy's mother told him to straighten up or he'd fall out of his chair. John straightened up so he'd look taller.
2. . to behave better. Bill was acting badly for a while; then he straightened up. Sally, straighten up, or I will punish you!
Make tidy, as in Let's get this room straightened up. [Second half of 1800s]
1. To stand erect: The drill sergeant ordered the recruits to straighten up when they started slouching in formation.
2. To put someone or something in order: I straightened up my bookshelves. The room was starting to look like a disaster zone, so we had to straighten it up. I hired a housekeeper to straighten up around the house once a week. We need to straighten up before your parents arrive.
3. To begin behaving properly: The principal cautioned the students to straighten up or face suspension.