a receptacle or one of a series of pigeonholelike slots, as in an office, into which incoming mail is placed for pickup.
Origin of mail drop
First recorded in 1970–75
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for mail drop
mainly US and Canadian a receptacle or chute for mail
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012