ˈdrop-in adjective [only before noun]
a drop-in place is a place offering a service or support where you can go without having to make arrangements first:
a drop-in advice centre

[TahlilGaran] Dictionary of Contemporary English ▲

drop in
to visit briefly.
About 100 guests dropped in to celebrate the publication of his book.

[TahlilGaran] English Idioms Dictionary ▲

drop in
to make a short or unplanned visit to someone
I decided to drop in on my friend after I finished work for the day.

[TahlilGaran] English Idioms Dictionary ▲

drop in
v. To make a short or unplanned visit; pay a call.
■ Often used with "on".
We were just sitting down to dinner when Uncle Willie dropped in.
The Smiths dropped in on some old friends on their vacation trip to New York.
Synonym: DROP BY, RUN IN².

[TahlilGaran] English Idioms Dictionary ▲