spontaneous occlusion of the circle of Willis
noun [ U or C ] medical specialized uk/spɒnˌteɪ.ni.əs əˌkluː.ʒən əv ðə ˌsɜː.kəl əv ˈwɪl.ɪs/ us/spɑːnˌteɪ.ni.əs əˌkluː.ʒən əv ðə ˌsɝː.kəl əv ˈwɪl.ɪs/
大脑动脉环特发性闭塞
a very rare condition caused by blocked arteries in the circle of Willis (= a ring of arteries at the base of the brain)