This is a pictograph of a goblet with a pointed base. The little roof shape represents a lid.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-354 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 88: Collections in India: Suomalainen Tiedeakatemia.
Comments:
There is only one extant example of this Indus sign.
The goblets may have been disposable. This is the case with some earthenware cups in Pakistan and India today. The Indus goblets were made very quickly on a fast wheel¹. This often resulted in a bend in the pointed base.
Image Credit:
Indus Script Sign Number 1403: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.
Note:
1. Jonathan Mark Kenoyer: Pointed Base Goblets: https://www.harappa.com/slide/pointed-base-goblets: Accessed: 25 October, 2017.