An unforeseen event is a sudden and unexpected occurrence that can disrupt plans and cause inconvenience. Synonyms for the phrase include "unexpected incident," "unanticipated situation," and "unforeseeable happening." Other options include "surprise occurrence," "random circumstance," and "unplanned event." These synonyms convey the idea of something happening unexpectedly and without prior notice. In addition, synonyms such as "accident," "calamity," and "disaster" suggest a more serious consequence resulting from the unforeseen event. In summary, there are various synonymous expressions for the term "unforeseen event," all of which convey the idea of an unexpected and unpredictable occurrence.