A wilfully stupid person is a person that pretends to be unable to work something out.
(Maybe they can work things out but they are too lazy to do so)
A wilfully ignorant person is a person that pretends not to know something.
(They either know it full well but pretend not to. Or they have chosen to erase it from their memory by not allowing it to occupy enough time therein to be committed successfully)
A genuine stupid person is a person that, try as they might, can’t work something out.
A genuine ignorant person is a person that, probably via genuine stupidity, and despite living in the age of information-saturation, has managed to filter out and discard most of the information flowing through his or her senses, leaving that which suites their one-track lives.
A stupidly wilful genuine ignoramus person is a person that works something out wrong, then expects to get full credit for the effort.
A genuinely stupendous Wil Wheaton person is Wesley Crusher saving the ship, but having difficulty getting laid.
A genuwilful stupignorant person is a person that uses Mental Floss to remove information which sticks in the synapses, fearing that such information may cause Truth Decay.
Hmm… I’ve always defined willful ignorance as when an individual seems to go out of their way to remain ignorant about something (usually a particular topic). For example, someone who believes that some bogus thing or another is true, but refuses to consider some evidence that might show them wrong. Like… creationists, as an extreme example.