Lexicography as a science, as much as it is modernized, it always is late (sometimes it is late more, sometimes less) with the fixation of the units, recently appeared in the language. The lexicographer deals with denotative neologisms: newly coined words, which belong to one author and an individual context. Semantic neologisms are frequent as metalanguage units and they can be found in belles-lettres contexts. The present article is a short essay about the classification barriers, fixation barriers and definition barriers of neologisms with their full diversity. Nowadays, French lexicography reaches high realizations in editing special dictionaries of stylistic neologisms and individual lexical creations including contextual semantic neologisms.