on-call
segment of time in which a worker is expected to be available at short notice to perform unpredictable work, or the status of such a worker
en-GB/ˈɒn - ˈkɔːl/
en-US/ˈɔn - ˈkɔl/
segment of time in which a worker is expected to be available at short notice to perform unpredictable work, or the status of such a worker