Domino effect is when one thing leads to another. Imagine a row of dominoes lined up in a row. If you push the first domino, it will hit the second one and it will hit the third one, and so on. This is like the domino effect because one thing (knocking over the first domino) led to a chain of other things (knocking over all the other dominoes). In everyday life, when something happens it can cause a chain reaction of other events - this is the domino effect.