oncall
adjectiveUK /ˌɒnˈkɔːl/
US /ˌɑːnˈkɔːl/
Being ready to work or help if someone needs you, even at night or on weekends.
The doctor is oncall tonight, so she keeps her phone close.
OTHER MEANINGS
2. A period of time when a worker must be ready to respond if needed.
He has a long oncall this weekend.
3. In computing, a system or person that is always ready to handle alerts and problems.
The engineer joined the oncall rotation for the new service.
4. Available for immediate help in an emergency.
The hospital keeps an oncall team for urgent cases.