infiltration
UK: ˌɪnfɪlˈtreɪʃən | US: ˌɪnfɪlˈtreɪʃən
n. the act of secretly entering or gaining access to a place or organization, especially for hostile purposes
n. the process of a substance passing gradually into or through something (e.g., liquid infiltrating a porous material)
n. (Medicine) the diffusion or accumulation of abnormal substances in cells or tissues
The word "infiltration" originates from the Latin infiltrare, combining in- (into) and filtrare (to filter). The root filtr- derives from Medieval Latin filtrum, meaning "felt" (a material used for filtering liquids). Over time, the term evolved metaphorically to describe both physical seepage (e.g., liquids passing through barriers) and covert human actions (e.g., spies entering enemy territory). The suffix -ation standardizes it as a noun denoting a process or result.
The military detected enemy infiltration across the border.
Water infiltration caused damage to the building's foundation.
The doctor noted signs of fat infiltration in the liver tissue.
Spy agencies often train agents in stealthy infiltration techniques.
Soil infiltration rates are critical for sustainable agriculture.