Slang for 4-HO-MET, a lesser-known novel psychedelic of the Tryptamine class (which includes substances like melatonin, serotonin, DMT and Psilocin). Users typically describe Schleeb as a more recreational version of psilocybin mushrooms due to its less serious headspace and greater emphasis on visual effects.
John: "YoBilly you tryna shnort this schleeb?"
Billy: "Hell yes John lets shnort this schleeb!"
When one partakes in the act of inhaling cocaine through the nostril. The "hoover" section of the saying comes from the vacuum brand, while schneef is a variation on the word sniff or to sniff. "Schneef" is slang for cocaine.
I'm so drunk, someone needs to rack up so I can hoover some schneef right now.
I'm surprised we're not hoovering some schneef right now!