The Indus Dictionary Project
This is the verb to trade with the addition of tracks oriented from the north to the south. It is an ideograph for the flow of traffic along the north south trade route. The meaning is therefore, north south trade route.
Lothal: Seal: L-86 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 258: Collections in India: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus sign.
It is interesting that this Indus symbol should have been found at Lothal, where the sea trade route was indeed roughly north to south, whilst the many examples of the symbol for east west trade route were found at either Harappa or Mohenjo-daro.
North South Trade Route: Lynn Fawcett, 2017.