any of various stones, fossils, prehistoric implements, etc. formerly thought to have been hurled to earth by lightning and thunder
- Any of various mineral concretions, such as a belemnite, formerly supposed to be thunderbolts.
- Archaic A flash of lightning conceived as a stone; a thunderbolt.
- (archaic) A thunderbolt.
- A stone or fossil of a kind once thought to be fallen thunderbolts.