- a person who or thing that pays an unexpected or uninvited visit: a feeder for squirrels, raccoons, and other drop-ins.
- a social gathering at which the guests are not expected to stay long: Be sure to stop by our house for a glass of eggnog at our Christmas drop-in.
- provided for short-term patronage: a drop-in shelter for people who are moving through homelessness.
- requiring only insertion to be ready for use: a drop-in battery pack.
- to intrude on a wave that another surfer is already riding
