The Indus Dictionary Project
This is the plural noun rooms or compartments with the addition of the noun container in one of the rooms. It is significant that the container is placed in the largest room. The container symbol can also represent the body of a cart. My inference is that lodgings, with an adjacent storage area, were being offered to merchants, in a similar way to that offered by caravanserai in more recent times. This would have enabled the merchant to ensure the safety of his precious cargo 24 hours a day.
Mohenjo-daro: Seal: M-952 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 92: Collections in Pakistan: Suomalainen Tiedeakatemia
This Mahadevan's sign number 243 which I have redrawn to better reflect the original. There is only one extant example of this Indus sign. Unfortunately, the inscription in which it occurs is incomplete.
Rooms with Storage: Lynn Fawcett, 2017.