Someone who is overly inclined to point out or complain about every flaw they come across (in or about something), no matter how small, petty, or insignificant. You might write me off as just a nit-picker, but you'll appreciate it when you get an A+ on this paper. This is why I hate going to the movies with nit-pickers like you. Instead of just enjoying what we watch, you have to criticize every little flaw you can think of!