theme song is a noun meaning "a melody used to identify a performer or a dance band or radio/tv program". It carries 2 recorded senses.
a melody used to identify a performer or a dance band or radio/tv program
a melody that recurs and comes to represent a musical play or movie
Definitions, synonyms and semantic relations for theme song come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.