What is the definition of herding in stock investment?

Herding is a term used to describe behaviour, very commonly used in behavioural economics. It suggests that human beings tend to operate in groups and are unwilling to go against the general consensus.

There have been many different theories surrounding herding, one of the most well known being cascading which says that all it takes is one well-informed investor to make a decision to cause all investors to follow him, on the assumption that he knows best.