Completely Full, Overflowing
A: Let's hang out at the bar
B: Nah, its pack out
'By the time we arrived it was already pack out'
2. Inebriated; drunk, under the influence.
Mariot suggested that they all go to Eeeemer's house, buy some drinks, and get pack out.
"Don't make fun of his faded purple suit, that's pack out."