Definition of subingression in English:
subingression
noun (ˌ)sʌbɪnˈɡrɛʃn(ˌ)sʌbɪŋˈɡrɛʃn
rare Subtle or unobserved entrance. Also: an instance of this; (in later use concrete) a secret or hidden entrance.
Origin
Mid 17th century; earliest use found in Walter Charleton (1620–1707), physician and natural philosopher. From sub- + ingression.