the egg or young form of a louse or other parasitic insec Meaning, pronunciation, example sentences, and more from Oxford Dictionaries. nit noun (PERSON). . › [ C ] UK informal disapproving a nitwit. Thesaurus: Synonyme und verwandte Wörter. Stupid and silly people · a right one idiom. Nit definition, the egg of a parasitic insect, especially of a louse, often attached to a hair or a fiber of clothing. See more.