1. return to what was just previously said/done; wait before continuing further
back up there for a second while I catch up
To 'back up' in a vehicle or movement means 'to reverse'. In a less literal context, it can be used to ask someone to repeat something or to go over information or instructions again. It is commonly used in social contexts by someone listening to an explanation or story, where the person listening has a question or needs to interrupt to clarify the information or fact. This can be used in social or professional contexts but is a little informal and certainly less polite than asking someone to repeat something or asking for clarification directly. You could also say 'Hold up' or 'Hang on' a second/minute.