1. a large dark nebula in the southern sky, visible as a dark patch against the Milky Way
Usage: astronomy; often capitalized as 'Coalsack'
2. a sturdy bag or sack used for carrying or storing coal
Usage: historical; industrial

Examples

• The Coalsack is one of the most prominent dark nebulae visible from the Southern Hemisphere.
• Astronomers use the Coalsack as a reference point when mapping the southern sky.
• Workers loaded coal into coalsacks for transport to the factory.
• The dark patch known as the Coalsack appears to cut through the bright band of the Milky Way.
• In the 19th century, miners carried their coal in sturdy coalsacks.
• The Coalsack nebula is located in the constellation Crux.