infiltration

Secretly entering a place or group, often to collect information or cause harm.

• The guards watched for enemy infiltration.
• Police infiltration of the gang took months.
• Better security could prevent infiltration by foreign agents.

How to use it: infiltration of something (The infiltration of the group went unnoticed.); infiltration by someone (The files revealed infiltration by undercover officers.)

Similar words: penetration

Common phrases: enemy infiltration, infiltration of something, prevent infiltration

The process of liquid moving into soil, tissue, or another material through small spaces.

• Rain increased water infiltration into the soil.
• Clay soils often have a low infiltration rate.
• The test measured fluid infiltration into the tissue.

How to use it: infiltration into something (Cracks allowed water infiltration into the walls.)

Similar words: seepage

Common phrases: water infiltration, infiltration rate, infiltration into something