When something is not in operation, it means that it is not currently functioning or in use. There are various synonyms that can be used to describe this condition, including idle, inactive, dormant, nonfunctional, out of order, off-line, unused, and out of commission. Idle implies not being used for a period of time, whereas inactive suggests a temporary suspension of use. Dormant refers to something that is in a state of temporary inactivity but may be activated in the future. Out of order means something is not working correctly, and nonfunctional suggests a complete lack of function. Off-line indicates something is temporarily disconnected from a network, and out of commission describes something that is no longer functioning due to maintenance issues or damage. Unused refers to a state of disuse rather than malfunction.