There are several synonyms for the phrase "keep someone waiting." These include delay, linger, linger behind, loiter, procrastinate, stall, tarry, and procrastinate. Other options include making someone wait, holding someone up, keeping someone at bay, and putting someone off. While some of these synonyms have negative connotations, they all imply that the person is not respecting the other person's time. It's important to be mindful of others and try to be punctual whenever possible. By being respectful of others' time, we can build stronger relationships and avoid unnecessary frustrations.