a group of events that happen in a particular order, one following the other, and are often repeated: the life cycle of a moth 蛾的生命週期. circulation uk / ˌsɜː.kjəˈleɪ.ʃən/ us / ˌsɝː.kjəˈleɪ.ʃən/ C2 noun. the movement of blood around the body: Exercise helps to improve circulation.