Looking for small or unimportant errors or faults, especially in order to criticize unnecessarily.A nitpicker is a person who finds faults, however small or unimportant, everywhere... moreLooking for small or unimportant errors or faults, especially in order to criticize unnecessarily.A nitpicker is a person who finds faults, however small or unimportant, everywhere they look. After seeing a movie, a nitpicker lists every tiny thing he or she didn't like about it. Use the informal nitpicker when you're talking about someone who is extremely critical, even when those criticisms seem inconsequential.