Englishunexpected
adjective
he received an unexpected invitation from Professor Dobson:
unforeseen, unanticipated, unpredicted, not bargained for, unlooked for, unhoped for, out of the blue, without warning, without notice;
chance, fortuitous, unplanned, serendipitous, adventitious;
sudden, abrupt, surprising, startling, astonishing, uncommon, abnormal, extraordinary;
North American, informal backasswards.
▷antonyms expected, predictable.
unexpected Oxford Dictionary of English