What does "#1 hit" mean?

1. Definition (n.) the most popular song in the country
Examples Britney Spears has the #1 song right now.
Examples Britney Spears has the #1 hit right now.

1. Definition (n.) the most popular song in the country
Examples Britney Spears has the #1 song right now.
Examples Britney Spears has the #1 hit right now.