Skull and crossbones

A skull and crossbones is a symbol consisting of a human skull and two long bones crossed together under or behind the skull. The design originated in the Late Middle Ages as a symbol of death and especially as a memento mori on tombstones. Actual skulls and bones were long used to mark the entrances to Spanish cemeteries (campo santo).

In modern contexts, it is generally used as a hazard symbol, usually in regard to poisonous substances, such as deadly chemicals.

It is also associated with piracy and software piracy, due to its historical use in some Jolly Roger flags.