infiltration
n. C / Un. the process of secretly entering a place or group to get information or cause trouble. It can also mean liquid slowly soaking into something like soil.
n. the action of entering or gaining access to an organisation or place surreptitiously, especially for espionage or subversion. In a physical sense, refers to the process by which a fluid passes into the pores of a substance.
The spy's infiltration of the enemy base was successful.
Security experts warned that the infiltration of the computer network likely began months before the data breach was discovered.
The heavy rainfall led to rapid infiltration of the parched soil, though the volume eventually exceeded the ground's capacity, resulting in significant surface runoff and local flooding.
From Middle English infiltracioun, from Medieval Latin infiltrātiōnem, infiltrātiō. By surface analysis, infiltrat(e) + -ion.
Uncountable when referring to the general process; countable when referring to a specific instance or event.