v.1. To have one's feeling of intoxication subside: I waited until I had sobered up and then drove home.
2. To cause someone's feeling of intoxication to subside: The jailer grabbed a pail of water and a cup of coffee to sober up the drunk. That nap really sobered me up, but I still have a hangover.
3. To overcome an alcohol or drug addiction: It wasn't until I had sobered up that I was able hold a steady job.
4. To become serious, grave, or solemn: Everyone sobered up and felt ashamed when they heard the bad news.
5. To make someone or something serious, grave, or solemn: The news of the disaster sobered them up. The accident sobered up the workers, reminding them how dangerous their job was.