The symbol of crossbones is often associated with death.
pirate
Frequency:
70
%
The costume included a pirate hat and crossbones.
danger
Frequency:
60
%
The warning sign had a symbol of crossbones to indicate danger.
Idiomatic Expressions for crossbones
Phrase: Jolly Roger
Meaning: a black flag with a white skull and crossbones, used by pirates
Usage: The pirates raised the Jolly Roger as they approached the merchant ship.