Unscheduled overtime is a term often used in the workplace to describe additional hours worked beyond the regular schedule. However, there are several other synonyms you can use to describe the same phenomenon. One of which is "unplanned overtime," which conveys an idea of a sudden and unexpected need to work additional hours. Another synonym is "emergency overtime," which implies an urgent need to complete a task or meet a deadline. "Unexpected overtime" is another synonym that denotes a need for additional work that wasn't planned in advance. Lastly, "surprise overtime" conveys a feeling of being caught off guard by the need to work extra hours.