syncope
noun [ U ] medical specialized uk/ˈsɪŋ.kə.pi/ us/ˈsɪŋ.kə.pi/ (also fainting episode)
晕厥
a short period of time when a person becomes unconscious
Postural syncope occurs when the body cannot supply enough blood to the brain in the upright position because of low blood pressure. 直立时因血压过低导致大脑供血不足时会出现直立性晕厥。