Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
gut feeling, gut course, gut reaction, gut response (nn.)
Each of these locutions is a slang idiom. Gut feeling, gut response, and gut reaction describe immediate and instinctive feeling, response, and reaction, relatively uninfluenced by thought. (Visceral is sometimes used as a euphemistic synonym for gut.) A gut course is an academic course that requires little effort from the student.
