Piloti (ピロティ) – in a given structure, a piloti is the ground-floor section that is supported primarily on columns so as to provide an “open-air” feel. Pilotis are generally wall-less on at least 2 sides, with the columns visible and prominent. However, a piloti can exist within the walled space of a larger enclosure such as the peripheral glass walls of a downtown skyscraper. They can be used for anything from gardens to parking lots to pools to recreational spaces.
Note that the English definition of piloti is simply the column itself, not the entire space associated with it. Here in Japan, we like to take foreign words and attach our own definitions sometimes.