Imagine a person standing in front of a bright sunset. You can't see the person's details, but you can see the dark outline of their shape against the bright orange sky. That person is silhouetted.
Here are some other ways to think of "silhouetted":
* A dark shape against a light background.
* A shadowy outline.
* A profile with no internal details.
* A shape defined by its edge.
Examples:
* "The mountains were silhouetted against the rising sun."
* "The dancer's graceful form was silhouetted against the stage lights."
* "The branches of the trees were silhouetted against the pale moon."