Most oncall refers to the person who is responsible for answering emergency calls and dealing with urgent issues outside of regular working hours. There are several synonyms that can be used to describe such a person. For instance, you can say that someone is the primary point of contact, the first responder, the emergency contact, or the go-to person when there's an urgent issue. Other words that can be used include standby personnel, the front-line worker, and the primary resource officer. All of these words help to convey the idea that someone is the most oncall person in a company, department, or team, responsible for responding to emergencies and resolving issues as quickly and efficiently as possible.