What does “infiltrate” mean in English?

You probably know “infiltrate” from spy films or news — agents infiltrate a building, a virus infiltrates the body. In this clip, a psychologist uses it for a painful emotion: “It takes over and infiltrates everything in your day.” That’s the surprise. The word means something quietly enters and spreads through — like ink in water. Once you spot it, you’ll hear it in politics, biology, and everyday talk.

In the clip, Dr Julie describes what happens the moment a painful emotion hits: “Instantly, it takes over and infiltrates everything in your day so that you can’t see anything clearly.” The image is an ink drop in water — it doesn’t stay in one place, it spreads through everything. That’s the heart of “infiltrate”: to slowly enter and spread, often without being noticed. You’ll also hear it in news (“protesters infiltrated the event”) and in science (“bacteria can infiltrate healthy body tissue”). It works in both writing and speech. The related noun is “infiltration” and the person doing it is an “infiltrator.”