This paper examines the different definitions of the term wild card. Most often the wild card is defined as a surprising event that has significant consequences. In the literature the examples labelled as wild cards do not always meet this definition. I have divided changes into two categories according to the rapidity of the change taking place: wild cards and gradual changes. By looking at the examples of wild cards in the literature, I found that a large number of them are actually gradual changes. This paper also clarifies the difference between wild cards and weak signals, which are sometimes considered synonymous. Weak signals are a means of avoiding blindness to gradual changes and wild cards in advance.