unanticipated
adj. B2 Upper Intermediate US //ˌənænˈtɪsəˌpeɪtɪd// UK //ʌnæntˈɪsɪpˌeɪtɪd// unan·tic·i·pat·ed
adj. not expected or planned for. You use this to describe something that happens suddenly and catches you by surprise.
adj. not foreseen or expected; occurring without prior warning or preparation. Often used in formal or technical contexts to describe unexpected outcomes or events.
The heavy rain caused unanticipated delays on the highway.
The sudden drop in interest rates led to unanticipated changes in the housing market that many experts failed to predict.
While the initial launch was a success, the software update introduced several unanticipated bugs that required an emergency patch to be released within forty-eight hours.