1. A shaft of lightning; a brilliant stream of electricity passing from one part of the heavens to another, or from the clouds to the earth.
2. Something resembling lightning in suddenness and effectiveness. The Scipios’ worth, those thunderbolts of war. (Dryden)
3. Vehement threatening or censure; especially, ecclesiastical denunciation; fulmination. He severely threatens such with the thunderbolt of excommunication. (Hakewill)
4. (Science: paleontology) A belemnite, or thunderstone.
(Science: zoology) Thunderbolt beetle, a long-horned beetle (Arhopalus fulminans) whose larva bores in the trunk of oak and chestnut trees. It is brownish and bluish-black, with W-shaped whitish or silvery markings on the elytra.