(1) A mispronunciation, used in polite company of the term "ball-assed".
Ball-assedness is the condition an otherwise fit, sleek and shiny mega-thru-hiker gets into after spending too many months off the trail, in town, at home, in front of the TV, eating crunchy salty snacks and over-replenishing the body's delicate electrolyte balance with uncountable cans of beer.
If you aren't now and never have been a mega-thru-hiker then it probably describes you too.
Roll on outta that chair and do some hiking. Or get me a beer too, 'K?
(2) Crushed rock, the original crunchy stuff.
It goes under railroad rails, and then it's called ballast.
First comes the road bed, an elevated surface, then the ballast, then the ties, then the rails, then lots of noisy trains.
The road bed is elevated to provide good drainage, and as a way of keeping the railway nearly level (trains don't like to go up or down steep hills).
Crushed rock is used as ballast because it drains water well, helps to spread the train's weight, and allows the track to settle in, while keeping down grass and weeds.
We should all be so perfect.
Hikers know ballast mostly from greenways, the conversion of old railroad rights-of-way into those peculiar linear parks.
Get to one before it's been paved and you'll see the ballast quietly hiding down there, dreaming of past glory.