Boyle refers to the scientific principle known as Boyle's Law, which describes the relationship between the pressure and volume of a gas. According to this law, when the temperature is held constant, the pressure of a gas is inversely proportional to its volume. This means that if the volume of a gas decreases, its pressure increases, and vice versa. The law is named after the Irish scientist Robert Boyle, who first formulated it in the 17th century. Boyle's work laid the foundation for modern chemistry and helped establish the field of gas laws, which are essential for understanding the behavior of gases in various conditions.