from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A storm sewer.
- n. A catch basin.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. 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
An allusion to their usefulness in catching stormwater and therefore preventing floods. (Wiktionary)