A strange phenomenon wherein a group of people plans a secret event to take place at a public location. The planning usually occurs online. Flash parties are usually silly, fun affairs.
A bunch of anime fans suddenly showed up at McDonald's wearing blue afro wigs and singing strange Japanese songs... flash party in action!
1. A description used for someone who has done better than you, for instance beaten you in a test or something similar. It is generally used when the other person is showing off and rubbing their glory into your face. It is slightly sarcastic and yet praising at the same time.
2. Also used for a description of something that is utterly amazing or cool, that is usually new and has never been seen before.
1. Amy: Yay! I got 25/25 in my Latin Test Jess!
Jess: Flash pants.
2. Hattie: Have a look at my new pencil case, Callum.
Callum: Wow, flash pants!
A social gathering on an "off night" of the week, usually at a bar or someone's house/apt, that starts out small but suddenly, unintentionally, and randomly reaches critical mass and turns into drunken mayhem.
"Last night McHugh and I went to the pub to have a few beers, but then people randomly started showing up and it turned into a flash party. Some Excedrin would be good about now."