This is a pictograph of water vapour. The symbol shares a common root with the Chinese character qì 气. Hence, it is the noun water vapour.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-1848 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 60: New material, untraced objects, and
collections outside India and Pakistan: Suomalainen Tiedeakatemia.
This is Mahadevan's sign number 120, which I have redrawn to better reflect the original.
In inscription M-1848, the symbol is used as an ideograph for clouds.