noun[ U ]medicalspecializeduk/ˌæk.tɪv səˈveɪ.ləns/us/ˌæk.tɪv sɚˈveɪ.ləns/
（医疗方面的）主动监测，积极监测，积极监察
a way of treating a medical condition that involves a period of waiting and regular testing, rather than immediate treatment such as surgery or chemotherapy