This is the symbol for road with a point of light at each corner of the character area. Each corner represents a cardinal direction, and a point of light signifies that something is true. In other words, something is true for roads in all places. Hence, it means roads everywhere.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-1923 e: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 83: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Comments:
There is only one extant example of this Indus sign.
In inscription M-1923, this character is not quite full height because it is written on one edge of the seal.
Image Credit:
Indus Script Sign Number 88: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.