Student or Learner
What is the meaning of Belly-to-Belly?
What is the meaning of Belly-to-Belly? This is not any sort of standard idiom. It sounds like two things pressed together, facing each other.
Back-to-Back? One after the other. The double feature shows two movies back-to-back
Head-to-Head? Direct competition.
Hand-in-Hand? Holding hands, or working closely together.
There are idiom dicionaries - you can look these up, you know. :)