Definition of "nullah"

About this time a large gole of horsemen came on towards me, and I proposed to charge; but as they turned at once from the fire of the guns, and as there was a nullah in front, I refrained from advancing after them.

1849, Brigadier Lockwood, Report of 2nd Cavalry Division at Battle of Goojerat

It was just after the exit from a bridge; the animal had probably come up out of the nullah.

1924 June 4, E[dward] M[organ] Forster, A Passage to India, London: Edward Arnold & Co.

Until a few years ago, much of the city’s sewage was released untreated into the Ganges via public drains, or nullahs, which discharged along the same bank as the ghats, where people habitually bathe.

2023 November 30, Oliver Franklin-Wallis, “Inside India’s Gargantuan Mission to Clean the Ganges River”, in Wired‎