Rupert's drop
noun
Ru·pert's drop
ˈrüpərts-
: a congealed blob of glass formed by dropping melted glass into water and setting up such residual stresses that the globule explodes violently when the surface is scratched or a piece broken off
Word History
Etymology
after Prince Rupert of Germany †1682 who first brought it to England to his uncle Charles I of England