Adiabatic circuits are low power circuits which use "reversible logic" to conserve energy.  Unlike traditional CMOS circuits, which dissipate energy during switching, adiabatic circuits attempt to conserve charge by following two key rules:
Never turn on a transistor when there is a voltage potential between the source and drain.
While this is an area of active research, current techniques rely heavily on transmission gates and trapezoidal clocks to achieve these goals.
^ "Adiabatic Logic", Benjamin Gojman August 8, 2004