leitmotif

‖ n. [ G., leading motive. ] 1. (Mus.) a guiding theme; in Wagnerian opera, a marked melodic phrase or short musical passage which always accompanies the reappearance of a certain person, situation, abstract idea, or allusion in the course of the play; a sort of musical label. Also called Leading motive. [ 1913 Webster +PJC ]

2. a recurring theme in the activities of a person or group. [ PJC ]