Literally means “fear of water”. Hydrophobic molecules are usually nonpolar, which is why they are repelled by polar substances such as water, and prefer neutral molecules and nonpolar solvents. Hydrophobic molecules in water will cluster together forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules: fats, oils, alkanes, and greasy substances.
The picture shows what happens when oil is poured into water; it doesn’t mix, but it creates two separate layers of liquids because nonpolar substances do not mix with polar substances.