A hollow, cylindrical metal armature covered in holes or slots, used as the backbone for large cylindrical cores in foundry work. The foundryman packs sand or loam around the outside to shape the core. The internal void and perforations allow expanding casting gases to vent safely out of the mold rather than blowing into the liquid metal.
Heard on the job
Wrap the lantern with straw rope before you pack the loam on, or it will never collapse during shakeout.