This is a pictograph of an adult person with outstretched arms. It is an ideograph for the adjective large or wide. The equivalent character in Chinese is dà 大.
Illustrative Text Reference:
Mohenjo-daro: Tablet: M-1429 A: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 194: Collections in Pakistan: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 1: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.