If two things are superimposable, it means they can be put on top of each other and look exactly the same.
This word is used in science and math to talk about shapes and objects that can fit exactly on top of each other.
Examples:
These two shapes are superimposable.
The two keys are superimposable.
The two pictures are superimposable.
My hands are superimposable!
The two buildings are superimposable, they look exactly the same!
The two puzzles are superimposable, they fit together perfectly.