past conjecture, unplanned, not bargained for, coming unaware, out of the blue, accidental, prodigious, unhoped-for, unpredicted, staggering, unhoped, unscheduled, unprepared for, stunning, unannounced, eye-opening, uncontemplated, wonderful, upset, unprovided for, amazing, not on the books, coming without previous intimation, forced, unlooked-for, unthought, like a bolt from the blue, electrifying, unthought-of, unsuspected, not in the cards, unheralded, fortuitous
sudden (part of speech: adjective)
surprising (part of speech: adjective)
- Sort of unexpected, wasn't it, Bill? - "The Coming of the Law", Charles Alden Seltzer.
- My sudden and unexpected appearance had frightened her. - "Kent Knowles: Quahaug", Joseph C. Lincoln.
- I must confess that I was struck with horror at the sudden approach of a death so new, so dreadful, so unexpected! - "The History of Sandford and Merton", Thomas Day.