monseigneur UK /ˌmɒnsɛˈnjəː/US /mɒnˈsinjəɹ/ noun2 •(no longer used) An honorific form of address for an eminent person in France, especially under the Ancien Régime. •(no longer used) (in particular) A title of the Dauphin of France. formsMesseigneurs · Monseigneurs · messeigneurs · monseigneurs