(in no particular order)
1. I'm going out with alot of people and I am too lazy to prattle off all of their names.
2. I am going to meet new people who I barely know
3. It's non of your business
4. These are people of ill-gotten-repute and I don't want you to know that I am hanging out with them.
also sinonomys with "just some friends", or "a few friends", etc.
Me: oh, just some friends...
Parent: ok, that sounds good, have fun