noun
blackwater
noun
1
Water that looks naturally dark because it carries dissolved organic matter such as decaying leaves or tannins.
"The blackwater rivers of the Amazon basin look almost like strong tea."
"Blackwater streams are common in swampy, forested lowlands."
2
Wastewater from toilets that contains human waste, as distinct from "greywater" from sinks and showers.
"The cabin's septic system separates blackwater from greywater for treatment."
How to Use Blackwater
Learner’s notesIn plain EnglishDark, tannin-stained natural water, or separately, sewage water from toilets.
Common mistake
Context tells the two meanings apart — river/ecology writing means the dark natural water; plumbing and sanitation writing means toilet wastewater.
Word Forms
blackwaters plural
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The _____ rivers of the Amazon basin look almost like strong tea.
Etymology
A compound of "black" and "water," describing water that looks dark rather than clear.