What term describes a substance that is repelled by water?

The term that describes a substance that is repelled by water is "hydrophobic." Hydrophobic substances are typically nonpolar, meaning they do not interact favorably with polar molecules like water. This results in a tendency for hydrophobic substances to avoid contact with water, often leading to behaviors such as clustering together in an aqueous environment.

In this context, hyrophilic substances, in contrast, are attracted to water and readily dissolve in it, making them water-loving. Amphipathic molecules possess both hydrophobic and hydrophilic portions, which allows them to interact with both water and lipids. Polar refers specifically to molecules that have a distribution of electrical charge that leads to partial positive and negative regions, influencing their interactions with water. Thus, "hydrophobic" is the precise term for substances that resist interaction with water.