A somewhat literary or old-fashioned term for a foolish or stupid person. Not as common in everyday speech as 馬鹿 (ばか) or 阿呆 (あほう).
He was so foolish that he was called a dunce.
There is a phrase 'a fool's dream'.
Composed of 痴 (ち, 'foolish') and 人 (じん, 'person'). The exact historical derivation is uncertain, but the kanji combination directly conveys the meaning 'foolish person'.