1. Order of architecture inferior to the dominant structural Order, as in Palladio's Basilica, Vicenza, where the subsidiary Order forms part of a serliana, and the dominant Orders carry the intermediate and crowning entablatures.
2. In Romanesque and Gothic doorways, with a series of Orders, the smaller or inferior Orders.
"sub-Order." A Dictionary of Architecture and Landscape Architecture. . Encyclopedia.com. (April 24, 2019). https://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/sub-order
"sub-Order." A Dictionary of Architecture and Landscape Architecture. . Retrieved April 24, 2019 from Encyclopedia.com: https://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/sub-order