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. The expert has his hand raised in greeting.
Mohenjo-daro: Seal: M-35 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 19: Collections in India: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus symbol.
Expert with his hand raised in greeting (based on Mahadevan's sign number 4): Lynn Fawcett, 2017.