Food poisoning: The illness resulting from eating food or drinking water containing poisonous substances including bacteria, viruses, pesticides, or toxins. Symptoms generally begin within 2 to 6 hours and include abdominal cramping, diarrhea, fever, headache, nausea, vomiting, and weakness.ood poisoning: The illness resulting from eating food or drinking water containing poisonous substances including bacteria, viruses, pesticides, or toxins. Symptoms generally begin within 2 to 6 hours and include abdominal cramping, diarrhea, fever, headache, nausea, vomiting, and weakness.