A skull and crossbones is a picture of a human skull above a pair of crossed bones which warns of death or danger. It used to appear on the flags of pirate ships and is now sometimes found on containers holding poisonous substances. Skull and crossbones stickers on the drums aroused the suspicion of the customs officers. A representation of a human skull above two long crossed bones, a symbol of death once used by pirates and now used as a warning label on poisons