1. See buttress; off-set. Also called set-off, scarcement, or weather-table.
2. Upper part of a building, e.g. a skyscraper, set back from lower storeys to enable light and air to reach the street below. Skyscrapers were sometimes built with several set-backs.
"set-back." A Dictionary of Architecture and Landscape Architecture. . Encyclopedia.com. (August 15, 2018). http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/set-back
"set-back." A Dictionary of Architecture and Landscape Architecture. . Retrieved August 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/set-back