Les Intraduisibles : nombriliste
Derived from the noun nombril, meaning ‘navel’ or ‘belly button’, and the adjectival suffix -iste, the term nombriliste refers to someone who thinks only of themselves, and takes no interest in the lives of others. So, for example, one might say ‘il est si nombriliste, il ne pense jamais à personne d’autre’ (‘he is so self-centred; he never thinks about anyone else’). This adjective can also be found in nominal form, in the word nombrilisme.
The word nombriliste refers implicitly to the saying se prendre pour le nombril du monde, which would translate into English as ‘to believe that the world revolves around you’. The slight difference in the imagery created by these two expressions is at the root of any difficulty you may have in rendering this adjective in English. Due to the fact that the English version of the phrase does not portray the person described as a particular ‘thing’, the nombril in this case, it is impossible to fully capture its meaning in a single adjective. We might try with terms such as ‘self-absorbed’ or ‘selfish’, and there is a noun, ‘navel-gazer’, which almost perfectly expresses the idea of being nombriliste, but this does not really work in adjectival form, and so the difficulty persists!