1. A short amount of time. Though the actual amount of time can vary, the phrase usually refers to a few minutes. Sir, your order will be ready in just a moment. When we get home, I'll need just a moment to change, and then we can go right back out.

2. interjection A request for someone to wait a short amount of time. Just a moment! I'll open the door as soon as I get dressed. OK, I just need to print out your receipt. Just a moment, please.