/drop"in'/ , n.
1. Informal. Also, dropper-in . a person who or thing that pays an unexpected or uninvited visit: a feeder for squirrels, raccoons, and other drop-ins.
2. Informal. 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.
adj.
3. provided for short-term patronage: a drop-in shelter for the homeless.
4. requiring only insertion to be ready for use: a drop-in film cartridge.
[ 1810-20; n., adj. use of v. phrase drop in ]