When one is so scared that they loose their pants. This in turn brings them higher up on the "Next-to-be-murdered list" in horror movies, a.k.a. the Horror Movie order.
This is a term used while you are bending down and picking upsomething off the floor and as you do so your pants get ripped or torn. Performing manual labor.
Danny B was loading some cigar boxes and all of a sudden he Screams out load "Fuck" and tells me. Dude I just " ripped the ass out of my pants" and I just bought them.