A device is a complex mechanical entity that may have some simple control modules but is not considered fully conscious or intelligent, ie is more primitive than a machine. Bashas are classed as devices, as they feel primitive plant-like emotions of pleasure or pain, they grow and repair themselves and have life-comparable housekeeping, but have no central mind. Scrolls are also devices.
It is also a derogatory term for a machine, usually used by prejudiced humans, and is the equivalent of calling a person an 'animal'.