self-acting

adj

adj

Etymology From self- + acting.

Acting of or by itself.

The door is fitted with a powerful spring and a feather-touch self-acting lock. It cannot be left unlocked unless you deliberately prop it open.1914, Ernest Bramah, Max Carrados:
On this railway there were three inclined planes of the self-acting type, the full wagons pulling up the empty.1947 May and June, “Notes and News: The Fordell Railway”, in Railway Magazine, page 188:

Entry derived from the Wiktionary, under licence CC BY-SA 4.0 — list of authors.