In this paper, we propose a simple methodology for building or extending wordnets using easily extractible lexical knowledge from Wiktionary and Wikipedia. This method relies on a large multilingual translation/synonym graph in many languages as well as synset-aligned wordnets. It guesses frequent and polysemous literals that are difficult to find using other methods by looking at back-translations in the graph, showing that the use of a heavily multilingual lexicon can be a way to mitigate the lack of wide coverage bilingual lexicon for wordnet creation or extension. We evaluate our approach on French by applying it for extending WOLF, a freely available French wordnet.