rainwater

• rain water

From Middle English reinwater, from Old English reġnwæter, equivalent to rain +‎ water. Cognate with West Frisian reinwetter, Dutch regenwater, German Regenwasser, Swedish regnvatten.

rainwater (usually uncountable, plural rainwaters)

1. Rainfall.
   • 2011 January 12, Joel Kirkland, “Australia's Record Rains Squeeze World Coal Supplies as Scientists Study Climate Pattern”, in The New York Times‎^[1]:

     In early December, as rainwaters had started the monthlong process of flooding mines and washing out rail lines, workers lined up before 1 p.m. at an easy-to-miss storefront depot in Mackay.

2. Water (for a house, etc.) sourced from rain which has not joined a spring, stream or river, pond, lake or sea.
   • 1987 January 18, Paula Deitz, “ISLAND LIVING, ENGLISH STYLE”, in The New York Times‎^[2]:

     Constructed of hard flint stone, which came as ballast from England and is now painted coral white, the house has a fishpond, or catchment, roof, dating from 1788, to collect rainwater.

• rainwater goods