A fork of Rural Dictionary
A man who's ass is just massive. So large that his fellow coworkers call him "Daddy Dumptruck", no matter the situation, and no matter who is around.
"Hey daddy dumptruck, can you grab me that pencil"
Literally the work center supervisor: "Yes, my son"
A man with large glutes, hamstrings and quads that he acquired throughout years of heavy squats and deadlifts.
There goes Michael again on the squat rack, no wonder he is such a Dumptruck Daddy.