Going out with the intent to entertain and be entertained by a group of admiring friends. Taken from the days of midevil royalty when the king would call his subjects for a big feast.
Maggie: "My phone is ringing off the hook and the texts are pouring in. Since we haven't been out in a week, everyone is desperate to see us."
Scarlett: "Oh, I know, same here."
Maggie: "I can go out Wednesday"
Scarlett: "Okay, it looks like we are holding court on Wednesday. I'll alert the subjects"
Hooking up refers to having sex, messing around refers to anything else (mostly beneath the waist) and making out is just making out. Done. Hooking up is having sex with no expectations or strings attached.
I was hooking up with this guy last night... means i was fucking this guy last night.
I was messing around with this guy last night... means I was giving him head/ he was going down on me.