used in reference to the consumption of alcohol, legal or not. Most often used when you don't want everybody and their mom around you to know your plans for the night.
A person--usually a married co-worker--that uses the company Christmas party as an opportunity to get extremely drunk and dance inappropriately on other co-workers' spouses, usually leading to embarrassment the next day.
Unruly hair that makes it look like the person has a party on their head. Often used to describe thick and long hair. Bares a very close resemblance to the term bed head.
I saw Mitch the other day. That guy has such party hair.
partypartyparty (also; party! party! party!) is a term used by an individual who's lifestyle encapsulates all that is chaotic and epic. Although alcohol may at times be involved, it is by no means necessary.
Partypartyparty is also commonly used as a universal cop-out or excuse for anything that is inexplicable, fitting all awkward (and non-awkward) scenarios.
Person A: "Hey man, why are you wearing a dress shoe and a Croc?"
Person B: "Because I partypartyparty."
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.