1. in a way that is sudden, loud, and forceful; with a loud crash or impact
Usage: informal; often used to emphasize the intensity or obviousness of something
2. in a way that is strikingly obvious or conspicuous
Usage: informal; used to emphasize how evident or unmistakable something is

Examples

• The cymbals crashed crashingly at the climax of the symphony.
• It was a crashingly obvious mistake that everyone noticed immediately.
• The door slammed crashingly shut behind him.
• Her silence was crashingly loud in the tense room.
• The stock market fell crashingly after the announcement.
• He made a crashingly bad first impression at the interview.