Synonyms for Unexpected (same or very similar meaning)
WordNet sense 1 (made necessary by an unexpected situation or emergency):
forced
WordNet sense 2 (not scheduled or not on a regular schedule):
unscheduled
WordNet sense 3 (not anticipated):
unforeseen, unlooked-for
WordNet sense 4 (happening without warning or in a short space of time):
sudden
From the ODE community, based on WordNet
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