If someone picks nits, they point out small, unimportant problems or faults in something. If I had to pick nits, I'd say the service could be a little quicker. That aside, it was pretty much perfect. Note: The verb nitpick has a similar meaning, and there is also a much more frequent noun nitpicking. The critics, of course, nitpick — that's what they do. The book was the subject of seemingly endless academic nitpicking. Note: Nits are the sticky eggs laid by the head louse, a small insect that lives and breeds in human hair.