The crossword solution for the term 'Word with Rain or Rock' is ACID. ACID is a type of chemical compound that has a sour taste and can corrode or dissolve other substances. It is composed of hydrogen and one or more other elements, such as oxygen, chlorine, sulfur, or nitrogen. Acids are found in nature, such as in rainwater, and are also produced synthetically. They are used in many industries, including food production, pharmaceuticals, and manufacturing.