mol ‧ ten /ˈməʊlt ə n $ ˈmoʊl-/ BrE AmE adjective [usually before noun]
[ Date: 1200-1300 ; Origin: An old past participle of melt ]
molten metal or rock has been made into a liquid by being heated to a very high temperature:
molten iron
molten lava (=liquid rock from a ↑ volcano )