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1. One who casually drops in, as to visit or obtain an appointment.
2. An informal social event.
Provided for short-term use: a drop-in center for runaways.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
1. Also, dropper-in. a person or thing that pays an unexpected or uninvited visit.
2. a social gathering to which guests pay a brief, informal visit.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.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.