A rock song is a type of popular music that typically has a strong beat and electric guitar riffs. The term 'rock song' can refer to a variety of genres, including classic rock, hard rock, and alternative rock. In this case, the crossword solution for the term 'rock song' is 'LULLABY, ' which is a gentle, soothing song typically sung to children to help them fall asleep. Lullabies often have a slow tempo and calming lyrics.