The Indus Dictionary Project
This symbol shares a common root with the Chinese character sī 糸. In modern Chinese, it is the noun silk. Xu Shen says that the symbol appears to depict a hank of yarn, and interestingly gives the archaic pronunciation as mò.
In Indus script, the symbol is comprised of two elements, the adjective fine and some threads. Hence, Mahadevan's sign number 4345 is the noun fine threads or fine yarn.
Mohenjo-daro: Seal: M-396 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 96: Collections in India: Suomalainen Tiedeakatemia.
Indus Script Sign Number 4345: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.