When you do something totally stupid or out of contest ruining a party or an official occasion!
Can be used also for smaller things like fall down on the street or expose parts of your body in public unintentionally, basically when you embarace yourself badly.
It's a word created in Latvia resembling a "french sound" but has nothing to do with french!
Yesterday I mada a lablamage, I cannot hold a smelling fart while on a meeting with my manager
I was speaking about how beach it is Sandy when I realize her housband was behind me, was such a lablamage!