This is an archaic symbol for water. It is the noun water.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-1834 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 58: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 132: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.