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latchkey child

noun
  1. a child who must spend at least part of the day alone and unsupervised, as when the parents are away at work.

Origin of latchkey child

First recorded in 1940–45; so called because such a child is provided with a key for getting into the home after school
Also called door-key child.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for latchkey child

latchkey child

noun
  1. a child who has to let himself or herself in at home on returning from school, as his or her parents are out at work
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