sinu-auˈricular,a.Zool. [f.sinu-, sinus + auricular a. 5.] Of or belonging to, situated between, the sinus venosus and the auricle. 1875Huxley in Encycl.Brit. I. 764/1 The sinu-auricular aperture, by which the sinus and the right auricle communicate,..has an oval form.