1. a salmon (Oncorhynchus nerka) of the Pacific coast that has a blue-black back, also called sockeye salmon
Usage: chiefly North American; also called blueback salmon
2. a type of herring or other fish with a dark blue or blue-black back
Usage: regional; informal

Examples

• The blueback salmon is prized by commercial and sport fishermen.
• Bluebacks migrate upstream to spawn in freshwater rivers.
• The fisherman caught several bluebacks during the summer run.
• Blueback salmon have distinctive red coloring during spawning season.
• Native peoples of the Pacific Northwest have harvested bluebacks for thousands of years.