The Indus Dictionary Project
This Indus symbol is comprised of two door leaves. The leaf on the right is set in the open position. Hence, Mahadevan's sign number 2125 is the noun open door. It can be likened to the Chinese character mǎo 卯.
Mohenjo-daro: Seal: M-678 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 35: Collections in Pakistan: Suomalainen Tiedeakatemia.
Mǎo is the earthly branch associated with spring. Given that inscription M-678 refers to altars, it is possible that Mahadevan's sign number 2125 was also associated with spring.
Indus Script Sign Number 2125: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.