ignoramus
Definitions
An ignorant or stupid person.
A person who lacks knowledge or education in general or in a specific subject.
Examples
The professor grew frustrated when the ignoramus in the back of the room kept interrupting the lecture with irrelevant questions.
It is difficult to have a productive debate with an ignoramus who refuses to acknowledge any facts that contradict their worldview.
He felt like a complete ignoramus when he realized he had been using the wrong tool for the job the entire time.