(colloquial, often used in the imperative, US) To wait.
Hey, wait up! I forgot my umbrella.
Wait-up Sentence Examples
On busy days, riders can wait up to an hour to get on this roller coaster, but because there are two tracks running at the same time, the wait most of the time is much shorter.
If you're buying an engraved ornament in a brick and mortar shop, you may have to wait up to an hour for it to be ready.
You may be tempted to pay for it because the alternative is taking time out of your day to drive to the vital records department, possibly stand in line, fill out a form and then wait up to an hour for someone to locate the record.
Expect to wait up to 10 business days for word on whether or not your application has been accepted.
Fred has a date with Mrs. Abernathy and won't be home for supper but wants you to wait up for him.