1. To acquire or move up to some better thing, position, rank, location, etc. After I got my tax refund, I decided to upgrade to a much better computer. I'm so happy we upgraded to first class—this is such a better way to fly!

2. To move or improve someone or something to a better or higher rank, position, grade, quality, etc. In this usage, a noun or pronoun is used between "upgrade" and "to." We've been upgrading the entire department to a new state-of-the-art security system. Forecasters have upgraded the storm to a level-three alert. We've upgraded you to the penthouse suite to make up for our error.