From Urban Dictionary:
Positive or negative expectations about circumstances, events, or people that may affect a persons behavior toward them in a manner that he or she (unknowingly) creates situations in which those expectations are fulfilled.
In other words, causing something to happen by believing it will come true
An employer sees a new employee and automatically expects him to be disloyal. The employer then treats the employee in a way to elicit the very response he concluded.
Labeling someone a "criminal," and treating that person as such, may foster criminal behavior in the person who is subjected to the expectation, thus creating a self fulfilling prophecy