infiltrate

To infiltrate is to enter a place, group, or system in a gradual or hidden way. Very often, it suggests secret entry with a specific purpose, like a spy slipping past security measures.

The word is often used in military, political, criminal, and technological contexts. A person can infiltrate an organization to gather intelligence, disrupt operations, or influence decisions from within. For example: "The journalist infiltrated the extremist group to expose their activities." Hackers may try to infiltrate a secure network, and undercover officers may infiltrate a gang.

Infiltration isn't limited to people and organizations. Ideas, trends, or even substances can infiltrate something else. "Social media is increasingly infiltrating our daily lives" suggests that it is slowly becoming a strong part of how we interact with the world. In a literal sense, you might say, "Moisture infiltrated the basement during the heavy rain."

The key idea behind infiltrate is moving into something in a way that is not open or obvious. With people or groups, it often implies secrecy, planning, and hidden motives. With ideas, trends, air, or water, it usually means spreading or passing into something little by little. Whether you are talking about spies, social change, or water damage, the word suggests entry that is hard to notice at first and important in its effects.