latchkey

noun, plural latch·keys.

1. a key for releasing a latch or springlock, especially on an outer door.

noun

1. a key for an outside door or gate, esp one that lifts a latch
2. 1. a supposed freedom from restrictions
   2. (as modifier)a latchkey existence

also latch-key, 1825, a key to draw back the latch of a door, from latch (n.) + key (n.1). Latchkey child first recorded 1944, American English, in reference to children who come home from school while both parents are at work.