Rainwater/ˈreɪnwɔːtər/ Definition 1 of 2Pro Tip 1/3Natural Source Rainwater refers to the natural water supply from the sky, often considered pure. Plants thrive on rainwater because it is free of chlorine. Pro Tip 2/3Outdoor Usage Rainwater is commonly mentioned in the context of outdoor activities or agriculture. We use rainwater to irrigate our fields. Pro Tip 3/3Conservation Efforts Collecting rainwater is often associated with environmental conservation and sustainability. They installed gutters to maximize rainwater collection.