Meantime refers to the time between two events or actions.
When we use "meantime", we often talk about what's happening while we're waiting for something else to happen. For example, if you're planning a trip but can't leave yet because of work, you might say, "I'll be tied up at the office meantime." This means that until your free time comes around (the future event), you'll be occupied with work stuff (the current situation).
The time spent waiting for another event; time in between.
Example: I'll get started tomorrow but, in the meantime, let's see if we can get a few more opinions.
During the interval; meanwhile
