Directly refers to chilling with no acquaintances or in short chilling alone. Referenced in the phrase “Billying no Bob” “Bob” referring to the friend that is not around.
Hilly-billing denotes the activity of sitting around a campfire while consuming large amounts of alcohol in the form of cheap beer that may or may not involve the smoking of oneherb or another. Other activities associated with hill-billying include making strange animal noises, awkward dances, and storytelling.
We'll be hill-billying in the backyard this weekend, you guys should come on over.