A system containing some quantity of water in a thermos flask or in an insulated beaker. This would not allow exchange of heat between the system and surrounding through its boundary. The process applied on the system is called

A thermo flask or an insulated beaker does not allow exchange of heat between the system and surroundings through its boundary. This type of system is called adiabatic system. The manner in which the state of such a system may be changed is called adiabatic process.