To support from below with props or masonry.
You should underpin the mine roof to prevent further collapse.
To give support to; to corroborate.
Public confidence in politicians must underpin our democracy.
A support or foundation, especially as a structure of masonry that supports a wall.
This house's underpinning is not up to standard.
A basis for something.
I would like to know more about the underpinning of this political theory.
The lower body or legs.