One who is ignorant.
"The ignorant student failed to answer the question because he had not studied the material."
uneducated in general; lacking knowledge or sophistication
"an ignorant man"
"nescient of contemporary literature"
"an unlearned group incapable of understanding complex issues"
"exhibiting contempt for his unlettered companions"
uneducated in the fundamentals of a given art or branch of learning; lacking knowledge of a specific field
"she is ignorant of quantum mechanics"
"he is musically illiterate"
unaware because of a lack of relevant information or knowledge
"he was completely ignorant of the circumstances"
"an unknowledgeable assistant"
"his rudeness was unwitting"
Unknowledgeable or uneducated; characterized by ignorance.
"The ignorant tourist had no idea that he was stepping on a protected historical monument."
In plain English: Ignorant means not knowing something important that you should know.
"He was ignorant about how to change a flat tire until his friend showed him."
Usage: Use ignorant to describe someone who lacks knowledge about specific facts rather than general intelligence, and avoid using it as an insult when you simply mean unaware. Distinguish this from words like clueless for casual situations or uninformed in formal contexts where a lack of information is the primary issue.
The word comes from the Old French ignorant, which was borrowed from the Latin ignōrāns meaning "unaware" or "unknowing." It entered English through this same path rather than being formed directly from its modern components in English.