What is "l'emmerdeur"

L'emmerdeur (English title: A Pain in the ...) is a 1973 French-Italian black comedy film starring Jacques Brel, appearing in his tenth and final feature film. Directed by Édouard Molinaro and co-starring Lino Ventura, Caroline Cellier, and Jean-Pierre Darras, L'emmerdeur is an adaptation of Francis Veber's 1971 play Le contrat.