One who casts off the restraints of a conventional life to pursue their passion(usually something dangerous and off the wall like base jumping, rock climbing, surfing etc.) Often you will find them living in vans, buses, caves or tents. Usually broke but always smiling.
Girl: Mommy, I never want to grow up. Mom: Well Dear, learn to climb, buy a van and become a dirtbagger.
by digital_vagabond November 04, 2015
One who prefers anal to other types of penetrative intercourse.
"Man, he is such a relentless dirtbagger. I don't know hoe he manages it!"
by Uncle Desmond December 09, 2003