When you 'blindside' someone, you do something they didn't expect which has negative consequences for them. It's not exactly the same as just a negative surprise, because it usually involves preventing them from achieving an expected goal or reaching a destination. You might think of this word in terms of motor racing, where the car behind the leader accelerates on the blindside (where visibility is low) and passes the lead car to win the race. In this scenario, the second car 'blindsided' the leader to achieve victory.

1. Jack didn't mean to blindside me with the news of David's death. He thought I already knew.
2. I was blindsided with the news of Henry's illness. it was very unexpected.

1. Staff were blindsided by the news that the business was under new management. Now no one is sure if their job is safe.
2. The boss didn't like me blindsiding him with the information, but there was no time to go through the proper channels.