The Indus Dictionary Project
This is a pictograph of a man with a banner attached to his head. It is an ideograph for the noun expert.
Mohenjo-daro: Seal: M-875 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 81: Collections in Pakistan: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus symbol.
A similar symbol to Mahadevan's sign number 4 can be found in the Naxi Dongba script. It is the Naxi word neng, which means ability, capable or can.
Indus Script Sign Number 4: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.