The adjective 'unprecedented' refers to something that has never existed or which has never happened in the past, something with no previous instance. This is a formal word used more often in professional contexts. Similar in meaning to 'unheard of' and 'unparalleled'. 

1. The student's outstanding exam results were unprecedented in the school.
2. After the match, the footballer took the unprecedented step of giving the media an interview.
3. The emergency alarm sounded when the temperature rose to unprecedented levels.

1. We have had unprecedented sales in the last quarter and our goal is to make the next one even more successful.
2. The fall in the economy is unprecedented and will have a huge number of knock-on effects.