1. To make new in appearance, style, or character; to update: Jessica modernized her kitchen with new paint, with a new stove and oven, and even with a microwave!
2. To improve or to adjust something in order to make it conform to present-day tastes, attitudes, or standards, or to be changed in this way: Jack's old car was modernized with new seat belts, a navigation system, and a stereo.

When Josie and Tim bought the old house they had to modernize the electrical system because it wasn't safe to use anymore.
3. To accept or to adopt to current ways, ideas, or style: The library in town has been modernized in that it not only offers books by modern authors, but it also has the newest videos, DVDs, and CDs for its customers.