A disgusting, sloppy vagina with sludge-like excretions (mucus, afterbirth, sperm, feces, etc). Likely accompanied by very foul odor.
A sludgina is what you might expect a wompus or a cheap hooker to have.
So I hooked up with this chick at the bar, but then I found out she had a sludgina!
This word has no inherent meaning but can be used in place of any word (sort of like fuck or smurf: smurf-berries, have a smurfy day, etc).
Chuckle is usually taken to mean the most perverse, obscene, or disgusting thing imaginable in the given context.