1- to "lay the mack down" on someone means to flirt with them, or hit on them
2- a Macki is someone who is very expirienced and smooth at picking up chicks
1- "Dude, I'm gonna go mack on that chick over there."
"That's my brother."
2- "Macki is super cool! I wish I could me more like Macki! I love Macki!"