The term involves hitting a person/persons named josh with an avacado. The avacado then explodes turning said avacado into guacamole. Thus producing a guacadossy.
Hey look at that guy named josh over there, lets smack him with an avocado. Call that a guacadossy.
Hey guy named josh you like avacados cuh?
Guy named josh: yea cuh You a guacadossy cuh.
n. A screenshot fabricated by a company to misrepresent the graphics of a game; a combination of the wordsbullshit and screenshot.
Originated from Penny Arcade, a popular gaming webcomic.
-Have you seen Madden 2006 for the Xbox 360? The graphics are gonna be awesome!
-Dude, the Madden 2006 images they showed at E3 were bullshots. It doesn't look nearly as good as they said.