Anything transformational has to do with a major change in the way something looks. If your dog is unrecognizable after her trip to the groomer, her haircut was transformational.
A radical change in the way something (or someone) appears is transformational, and the word's Latin root transformare fittingly means "change of shape." In technology, transformational is commonly used to describe computer languages that are designed to take data in one format and convert it into a different one. While the underlying information remains the same, it has been transformed in a way that makes it easier for people (or computers) to understand.