It's an eco round, you all buy a P90 and a flash and ass rush the fucking B site.
"Ight niggas it's time to full rush B" -some racist Russian
Grade-B Jackassery is a common form of "Jackassery" on a grading-scale starting from "Grade-A Jackassery", but is specifically one level lower in intensity.
"Come on Mr. Bucknell, that form of Grade-B Jackassery is not appreciated here."
"You know I was being a Grade-A Jackass, but James you can't be following my Jackassery with Grade-B Jackassery. It's just not the same thing."