obsolete A euphemism for any severe gastrointestinal infection, especially food poisoning or cholera, typically contracted by children in the summertime. Mary has a bit of the summer complaint, so she has taken to bed for the rest of the week. Before personal hygiene and food safety practices became commonplace, children became ill and died from what adults rather flippantly called summer complaints.
See also: summer
n. diarrhea, especially that experienced in the summer. I’ve got a touch of the summer complaint.