1. to take place or happen, be received or recorded in a particular way, fail or cease to function properly
I have no idea what went down at the party. I wasn't there.
Expression 'what's going down?' is an informal way of asking 'what is happening?' or 'what is going on?'. This is a predominantly American expression. In the past tense, you might ask 'what went down?' so you might ask 'what went down at the meeting yesterday?' or 'let me tell you what went down in the bar last night'. This is a casual expression but you can hear it in both social and professional environments.