Chess Glossary : Section X
X-Ray Attack
A sudden case of transparent research and look what the Chess Glossary Team found at Wikipedia … “In chess, the term X-ray or X-ray attack is sometimes used (1) as a synonym for skewer. The term is also sometimes used to refer to a tactic where a piece either (2) indirectly attacks an enemy piece through another piece or pieces or (3) defends a friendly piece through an enemy piece.“