skull and crossbones
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)