To stop and spend time at some place or with someone for a brief period of time. A noun or pronoun can be used between "stop" and "down." You should stop in for one of our poker games, they're a lot of fun!It was so great to see you, thanks for stopping in!
stop in
(some place) Go to stop by (some place).
stop in
see under stop by.
stop in
v.
To interrupt one's course or journey briefly in order to visit or do business somewhere: The next time you're nearby, stop in for dinner. I stopped in at the office on my way to the airport.