n., pl., skulls and crossbones.
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.
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.