You're a complete and utter ignoramus!
(You say it IG-n'RAYms. It's a very satisfying word for shouting.)
An ignoramus is someone who doesn't know as much as he should, and probably much less than he pretends. You find them (the plural is, sadly, ignoramuses) very regularly on television, in bars, driving taxis, teaching, tending to the sick, and trying to run banks and countries, and *
The first ignoramus was a lawyer, as it happens: but that must surely be the wildest possible coincidence...
Word To Use Today: ignoramus. This word is legal Latin for we have no knowledge of, from the Latin ignōrāre, to be ignorant of, but its modern usage comes from the title character in a play who was a lawyer. The play was written in 1615, mostly in Latin, by George Ruggle. It lasts six hours, but it was said to be 'full of mirth and variety,' and King James I enjoyed it so much he went to see it twice.
The play is an attack by academics on the non-classical Latin of lawyers. It caused a lot of fuss, and even to some changes to legal language.
*Do fill in your own examples from personal experience here.