Skull and crossbones

An skull and crossbones is an symbol consisting of an human skull and two bones crossed together under the skull, used as an warning for something that is dangerous or deadly, such as pirates or poison. Today, the skull and crossbones is primarily used for poison.

In the case of the use by pirates, the skull and crossbones commonly presented on a black field is one style of flag known as a Jolly Roger intended to strike fear in the crews of target ships (with the hope that surrender could be negotiated without a fight).