What term is used for highly decorative trim in architecture?

The term used for highly decorative trim in architecture is "entablature." An entablature is a horizontal structure that sits on top of columns and beams, consisting of three main sections: the architrave, frieze, and cornice. This architectural feature is often elaborately designed and serves both a structural and decorative purpose in classical architectural styles.

While frieze might refer to a decorative band that can be part of an entablature, it does not encompass the entire highly decorative trim aspect of architecture. Cornices are also decorative but specifically refer to the uppermost section of a wall, where it meets the roof. Baseboards function to cover the joint between the wall and the floor, serving more of a functional role than a highly decorative one. Thus, entablature captures the essence of extensive decorative trim effectively.