A vicious cycle (also known as vicious circle) is used to describe a situation in which events are in a feedback loop in which the action or event is strengthened by its consequence which starts the cycle all over again. It is an event pattern that never reaches equilibrium and is in constant motion.
Vicious cycle is used to describe a negative pattern of events while a virtuous cycle is the same pattern but has positive events or outcomes.
An example of a vicious cycle is poverty. An individual who lives in poverty has no money to improve their situation socially or by education. They have no money to pay bills resulting in late fees and high interest which make them more poor. Their children are raised in poverty with no access to educational advantages and fall into the same cycle as their parents.