skull and cross·bones
noun/ˌskʌl ən ˈkrɒsbəʊnz/
/ˌskʌl ən ˈkrɔːsbəʊnz/
[singular]- a picture of a human skull above two crossed bones, used in the past on the flags of pirate ships, and now used as a warning on containers with dangerous substances inside
骷髅旗，骷髅画（旧时画在海盗旗上，现在作为警示印在危险物品的容器上）