To go on a "vacation" or to go "vacationing" is when a person gets high enough to leave reality for days; sometimes even weeks.
"Man, you were fucked up for days!"
"Yeah I was tripping so hard that I took a vacation."
"Hey man, lets go vacationing."
"I'm down, you bring the brews, ill bring the buds; we'll bring the women, and they'll bring the drugs."