sinoatrial node Syllabification: (si·no·a·tri·al node)Pronunciation: /ˌsīnōˈātrēəl/Definition of sinoatrial node noun Anatomy a small body of specialized muscle tissue in the wall of the right atrium of the heart that acts as a pacemaker by producing a contractile signal at regular intervals. Origin: early 20th century: from sinus + atrial (see atrium)
