the egg or young form of a louse or other parasitic insec Meaning, pronunciation, example sentences, and more from Oxford Dictionaries. 2) In lighting, the nit is a unit of visible-light intensity, commonly used to specify the brightness of a cathode ray tube or liquid crystal display computer display. Define Nits. Nits synonyms, Nits pronunciation, Nits translation, English dictionary definition of Nits. abbr. National Invitational Tournament n. The egg of certain.