What is Sickness?

Legal Definition
By sickness is understood any affection of the body which deprives it temporarily of the power to fulfil iis usual functions.

2. Sickness is either such as affects the body generally, or only some parts of it. Of the former class, a fever is an example; of the latter, blindness. When a process has been issued against an individual for his arrest, the she-riff or other officer is authorized, after he has arrested him, if he be so dangerously sick, that to remove him would endanger his life or health, to let him remain where he found him, and to return the facts at large, or simply languidus. (q. v.)
-- Bouviers Law Dictionary
Legal Definition
Discase; malady; any morbid condition-of the body (including insanity) which, for the time being, hinders or prevents the organs from normally discharging their several functions. L B. 8 Q. B. 295.
-- Black's Law Dictionary