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]
a recurring theme in the activities of a person or group. [PJC]
leitmotif, n. (also leitmotiv) a recurrent theme associated throughout a musical, literary, etc. composition with a particular person, idea, or situation.