Wiktionary
n. (context US English) An access point or conduit for rainwater that drains directly downstream in a (drainage) basin without going through sewers or water treatment in order to prevent or belay floods
Wikipedia
A storm drain, storm sewer ( US), surface water drain/sewer ( UK), stormwater drain ( Australia and New Zealand), or simply a drain or drain system is designed to drain excess rain and ground water from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems. They are fed by street gutters on most motorways, freeways and other busy roads, as well as towns in areas which experience heavy rainfall, flooding and coastal towns which experience regular storms. Even the gutters from houses and buildings can be connected to the Storm drain. Many storm drainage systems are designed to drain the storm water, untreated, into rivers or streams. As a result, it is not okay to pour certain types of chemicals into the drains.
Some storm drains lead to a mixing of stormwater (rainwater) with sewage, either intentionally – in the case of combined sewers – or unintentionally.
Usage examples of "storm drain".
Apparently it was flushed out of a West Side storm drain, probably during a recent heavy rain.
The tale was about a bank robber who killed two people during a holdup and then, fleeing police, slipped into the city's storm drain system.
But there were traces of industrial solvent where they'd removed the false red road markings from the top of the storm drain.
He felt his way across to the storm drain, aided by the growing, flickering light of the burning papers.
Reassured, he went on again, eased past a pile of garbage into a bigger alley that skirted the storm drain.
The storm drain was five feet deep and served normally for sewer, laundry or sink, depending on the amount of water therein.
Vaulting onto the flat section which turned out to be a covered storm drain, I glanced around.
The storm drain tunnels added a strange booming echo off walls and ceiling, and after half a mile he began to sing as he walked.