The term 'physically inactive' can be summarized by the word 'INERT, ' which is defined as 'not reacting or responding to a stimulus; motionless; lacking energy or vigor.' In other words, someone who is physically inactive is not engaging in any physical activity and is not expending any energy. This could be due to a variety of reasons, such as a lack of motivation, physical disability, or simply a preference for a sedentary lifestyle.