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  • rainwater
    rainwater
    noun
    water fallen as rain.
  • Rainwater
    Rainwater
    noun
    (Leo) James, 1917–86, U.S. physicist: Nobel Prize 1975.
Synonyms

rainwater

1 American  
[reyn-waw-ter, -wot-er] / ˈreɪnˌwɔ tər, -ˌwɒt ər /

noun

  1. water fallen as rain.

Rainwater 2 American  
[reyn-waw-ter, -wot-er] / ˈreɪnˌwɔ tər, -ˌwɒt ər /

noun

  1. (Leo) James, 1917–86, U.S. physicist: Nobel Prize 1975.

rainwater British  
/ ˈreɪnˌwɔːtə /

noun

  1. water from rain (as distinguished from spring water, tap water, etc)

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of rainwater

before 1000; Middle English rein water, Old English regn-wæter; see rain, water

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

He avoids bottled water due to microplastics and has set up an elaborate system to catch rainwater from the house roof.

From Slate • Mar. 30, 2026

Oil fires can also release sulphur and nitrogen oxides, which can form acids if they dissolve in rainwater, as well as other harmful hydrocarbons, metallic compounds and droplets of oil.

From BBC • Mar. 10, 2026

As of December, its dams were only around 30 percent full on average, and farmers have largely relied on rainwater for irrigation.

From Barron's • Feb. 13, 2026

These included data from Arctic ice-cores and rainwater samples collected around the world.

From Science Daily • Feb. 6, 2026

It was winter, with a skim of ice across the rainwater.

From "Secrets at Sea" by Richard Peck

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.