The domino effect is a phrase that describes a chain reaction that occurs when an event sets off a series of similar events. There are many synonyms for the domino effect, including a ripple effect, a butterfly effect, or a chain reaction. These phrases all describe a situation where one small action can have a big impact on other related actions. Other synonyms for the domino effect include the snowball effect or a knock-on effect. All of these phrases capture the idea of a small initial cause leading to a much larger and potentially unpredictable set of consequences.