The Ferguson reflex, also known as the rectoanal inhibitory reflex (RAIR), is an automatic reflex that occurs when the rectum is distended by feces. This reflex is important in defecation, as it relaxes the internal anal sphincter and opens the anal canal to allow for the passage of feces. Synonyms for the Ferguson reflex include the rectoanal reflex, the anorectal reflex, and the defecation reflex. While these terms may have slightly different meanings in certain contexts, they all refer to the physiological process of rectal distension triggering a reflexive relaxation of the internal anal sphincter. Understanding the Ferguson reflex is important in the diagnosis and treatment of various gastrointestinal disorders.