If you've ever been afraid to speak up in class, you might be worried that you'll look like an ignoramus, or an uneducated, ignorant person.
Calling someone an ignoramus is an insult — it's a colorful way to comment on a person's ignorance or stupidity. The word comes right from the Latin ignoramus, literally "we do not know," which was a legal term in the 16th century that could be used during a trial when the prosecution presented insufficient evidence. After George Ruggle's 1615 play "Ignoramus", it came into popular use to mean "fool" or "dunce."