The act of drinking too much and letting all your skeletons out of the closet. Consuming so much alcohol that you can't lie. Giving others alcohol to get their guards down and answer questions truthfully.
"he truth slurummed all over her last night and she thinks he's a freak"
"going to buy some truth slurum to have during dinner and question him"
"didn't mean to freak you out last night, guess I had too much truth slurum"