To lose control of oneself, utterly and completely, and to exude douche.
Named for Spencer Pratt's behavior on the Mtv reality show The Hills.
"what the fuck were you THINKING forgetting to roll my car windows up homie?!! don't you read the weather report?? FUCK!!!"
"dude, you're spencing out. be cool."
The name given to those who act out immaturely, like Spencer Pratt's meltdown on I'm a Celebrity, Get my Out of Here.
Person #1: "Oh, boohoohoo! Blah, blah, blah!"
Person #2: "Dude, you're totally Spencing Out."