A subtext is a hidden or non-obvious meaning to something. It's a term from literary criticism that has become more mainstream. The idea is that a work of art has a meaning that is obvious, or overt, but carries other, perhaps unintentional, meanings.
So, you might watch a Roadrunner cartoon; on the surface, it's just a funny cartoon, but its subtext could be interpreted as:
- Violence is fun.
- Violence is bad. If you try to hurt someone else, you will hurt yourself instead.
- It's OK to laugh at unlucky, starving people.
- Relying on technology is dangerous.
- When we try too hard, we fail.
You could also refer to the subtext of a situation, like a business meeting, a political rally, or a drunken frat party. Ah, the joys of semiotics.