What is 1d10t?
One Delta Ten Tango, or "1D10T" is a military acronym used to describe an idiot, when speaking to that particular idiot, specifically because he/she is an idiot. Usually spelled out phonetically in order to confuse said idiot.
SGT: Your new career field is 1D10T, or One Delta Ten Tango, Private.
Private: Uh, what's that mean, Sergeant?
SGT: (sigh) Never mind.