dumb terminal = D = dumbed down

dumbass attack /duhm'as *-tak'/ n.

[Purdue] Notional cause of a novice's mistake made by the experienced, especially one made while running as root under Unix, e.g., typing rm -r * or mkfs on a mounted file system. Compare adger.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.