latchkey

Noun

 * 1) A key, especially to an outside door.
 * 2) A child who is given a key to the home and is expected to remain at home alone (without adult supervision until the parents return from work).
 * 1) A child who is given a key to the home and is expected to remain at home alone (without adult supervision until the parents return from work).

Adjective

 * 1) Equipped with a key; generally in the phrase latchkey child.