Adiabatic expansion refers to the process in which a volume of gas expands without gaining or losing heat. Some synonyms for this term include isentropic expansion, reversible expansion, and adiabatic cooling. These terms describe the same process in slightly different ways. Isentropic expansion implies that the change in entropy during the process is zero, while reversible expansion suggests that the process can be reversed without any loss of energy. Adiabatic cooling emphasizes the fact that the temperature of the gas decreases during the expansion. These synonyms are frequently used in thermodynamics and can be helpful in understanding various physical phenomena related to heat and energy.