Step 1: Understanding the Concept:
Gastrointestinal malabsorption disorders alter fecal composition and macroscopic appearance.
Step 2: Detailed Explanation:
Steatorrhea is the clinical term defining the excretion of abnormal quantities of unabsorbed fat in feces, resulting in bulky, pale, greasy, and foul-smelling diarrhea.
It occurs due to pancreatic exocrine insufficiency (lack of lipase) or bile salt deficiency preventing fat digestion and absorption.
Steatitis is adipose tissue inflammation (yellow fat disease), and keratitis is corneal inflammation.
Step 3: Final Answer:
Hence, foul-smelling diarrhea containing fat is called steatorrhea.