Which word indicates a significant change in fashion that displaces the old?

The word that indicates a significant change in fashion that displaces the old is "revolutionary." This term is commonly used to describe changes that are not only impactful but also transformative, suggesting a complete overhaul of existing trends or styles. A revolutionary change typically means that the new idea or fashion replaces the older one entirely, emphasizing the radical nature of the shift.

In contrast, "persistent" describes something that continues steadily or remains constant over time, which does not align with the idea of displacing old fashions. "Ephemeral," while it refers to something transient or short-lived, does not convey the notion of significant change or replacement. Lastly, "static" implies a lack of movement or change, directly opposing the idea of a shift in fashion trends. Therefore, "revolutionary" is the most fitting choice, encapsulating the essence of a seismic shift in the fashion landscape.