A vicious cycle or a vicious circle is an expression that refers to a situation wherein a series of events occur in such a way that they perpetuate and worsen the problem, leading to a downward spiral. It's like a never-ending loop with no positive outcome, often characterized by self-reinforcing negative feedback loops or a cycle of cause and effect. The phrase is also used metaphorically to describe situations where there seems to be no way out, as the problem only leads to more problems in an endless chain reaction.