key·ing I. \ˈkēiŋ-ē.ēŋ\noun (-s) Etymology:key (I) + -ing (n. suffix) : the process of turning an electronic circuit off or on either manually or automatically < such keying represents the simplest possible form of modulation, and is applicable to all kinds of oscillators — W.A.Edson > II. adjective : possessing the ability to turn an electronic circuit off or on < a keying device >