The phrase "infirmity of body" refers to a physical weakness or ailment that limits one's abilities. There are numerous synonyms that can be used to describe this condition, including frailty, debility, weakness, disability, incapacity, infirmness, and vulnerability. Each of these words refers to a different aspect of physical limitation, such as a frailty that may come with age, a debility resulting from an injury or illness, or a weakness caused by a chronic condition. Overall, these synonyms can be used to convey a sense of physical vulnerability and the need for care and support to cope with the challenges of living with an infirmity of the body.