(figuratively, by extension) A process of finding or pointing out tiny details or errors, particularly if the pointed-out details seem insignificant or irrelevant to all but the finder.
“Only a mean-spirited nitpicker would draw public attention to unimportant or isolated textbook errors.”
“Although she declines to use the title, Abigail F. Rosenfeld, a thirty-five-year-old Borough Park mother of ten, is a nitpicker of extreme, if secret, renown.”
“According to some nitpicker at the Ohio Department of Education, Mrs. Roberta Erwin retired and left teaching entirely in 1967, Two years before my birth.”