drop in

Verb

drop in (third-person singular simple present drops in, present participle dropping in, simple past and past participle dropped in)

1. Used other than figuratively or idiomatically: see drop, in.
   • The keys were dropped in the fishbowl.
2. (idiomatic) To arrive casually and unannounced, with little or no warning; also, to visit without an appointment.
   • I was in the garden covered with mud when my grandmother dropped in for a visit.
   • We made an odd party before the arrival of the Ten, particularly when the Celebrity dropped in for lunch or dinner.1897 December (indicated as 1898), Winston Churchill, chapter V, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd., →OCLC

   Synonyms:

   drop by, pop in, stop by, stop in

3. (intransitive) To paddle into and take off on a wave another surfer is already riding.
   • Most beginners are blissfully unaware that dropping in on someone is a cardinal sin.2003, Neal Miyake, “The Unwritten Rules of Surfing”, in (Please provide the book title or journal name), archived from the original on 14 Oct 2005
4. (intransitive) To fall in; to cave in.
   • ⁠The cheeks drop in; the body bows;
     Man dies: nor is there hope in dust: […]1850, [Alfred, Lord Tennyson], “Canto XXXV”, in In Memoriam, London: Edward Moxon, […], →OCLC, page 54
5. (US, transitive) To install components, particularly car engines.
   • We dropped in all-new parts in the sports car.