Final answer:
A substance that repels water is described as hydrophobic, meaning 'water-fearing'.
Step-by-step explanation:
A substance that repels water is called hydrophobic. The term hydrophobic comes from the Greek words hydro (water) and phobos (fearing). Such substances do not interact favorably with water because they are typically nonpolar, meaning they do not have a charge distribution that would attract them to the polar water molecules.
Examples of hydrophobic substances include oils and fats. In contrast, substances that mix with, dissolve in, or are wetted by water are described as hydrophilic, which means 'water-loving'.