The
act of relieving one's self (urinating)
outside. Typically the term is used by truck drivers and travelers who have driven many
miles (without a truck stop or rest area) and- needing to piss, they pull over to a side road to "squirt the dirt".
Damn, Frank bought that big-ass 200
ounce bladder
buster at the truck stop and the next thing
you know, we have to pull over to squirt the dirt.