v.1. To quickly or briefly enter some place on foot: I'm going to run in the house and get my jacket. We stopped at the store, and I ran in and bought some milk.
2. To drive someone to the center of a place: Don't walk all the way to town—I can run you in on my way to work.
3. Slang To arrest someone; take someone into legal custody: I had no identification with me, so the police ran me in. The police ran in the suspects for further questioning.
4. To make a solid body of text without a paragraph or other break: All of the paragraphs on this page run in, so it's very hard to read.
5. To cause some printed material to make a solid body of text without a paragraph or other break: The editor ran in the final paragraph so that it would fit on the page. There was no reason to split this text into two paragraphs, so I ran the second one in.