lofthead means an overhead cavity in a cave or mineshaft caused by a fall of roof. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Etymology
From loft + head.
noun
- An overhead cavity in a cave or mineshaft caused by a fall of roof.“If a certain vacant space is left above the timbering of a road, it often affords a lodgment for gas, and it is by no means easy to ventilate such a space, or, as it is often called, a "lofthead," in all cases.”