When a guy sits down in a seat and spreads his legs apart wide, as if his testicles were hot as lava and needed ventilation. Usually used pejoratively, especially against men who do this on public transit and so waste space or make their seat neighbors uncomfortable.
Ugh, I was on the T and this guy say down right next to me and was lavaballing halfway onto my seat! Rude and gross!
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.