When you're in a standby mode, it means you're ready and waiting for something to happen. But there are several synonyms for this phrase that can be used interchangeably. "On hold" is a commonly used phrase, which means you're pausing an action for some time. "In reserve" can also be used, indicating that something is held back for future use. "Available," "waiting in the wings," "in readiness," and "in a holding pattern" are other options, each with a slightly different connotation. However, they all convey the idea of readiness and preparedness for when the time comes. So, whether you're waiting for your flight, a phone call or completing an urgent task, you're always "on standby".