The term "water-insoluble" refers to a substance that cannot be dissolved in water. Some commonly used synonyms for this term are "water-repellent," "hydrophobic," and "water-resistant." Other possible synonyms include "non-aqueous," "waterproof," and "immiscible with water." These terms are often used in chemistry and manufacturing industries, where it is important to distinguish between substances that can be dissolved in water and those that cannot. Understanding the properties of water-insoluble substances is vital in controlling their behavior and ensuring that they are used safely and effectively.