a def posse is basically a loser word for cool or awesome group of close friends, usually used by losers and wangsters who want to act cool / people making fun of wangsters by acting like one
The international T-Pose day is on the 18th June and celebrates the famous T-Pose. You can celebrate it by doing the Pose and chanting the Halo Theme with your boys
A:Did you know today is the international T-Pose Day?
B: No dude let’s sing the Halo Theme and pose with the boys