The definition of a separate air conditioner is a unit that is not connected to a furnace or other central heating system. Instead, it is a self-contained unit that is installed in a room or area and is used to cool the air. It is typically powered by electricity and works by drawing in hot air from the room, cooling it, and then releasing the cooled air back into the room. This type of air conditioner is ideal for people who want to cool a single room or area without having to install a full central air conditioning system. It is also a great option for people who want to save money on their energy bills, as separate air conditioners are usually more energy efficient than central air conditioning systems.