This is the outline of an area to which the verb to hide has been added. Hence, the definition is a concealed space or a concealed area.
Illustrative Text Reference:
Dholavira: Stone Block: R.S. Bisht, 2015: 8.1.2 Inscription on a Stone Block, Fig. 8.8: Excavations at Dholavira (1989-90 to 2004-2005), p. 230: https://www.scribd.com/document/262316120/Excavations-at-Dholavifra-1989-2005-RS-Bisht-2015: Accessed: 17 November, 2018.
Image Credit:
Concealed Area: Lynn Fawcett, 2018.