1. a body louse, especially one that infests humans
Usage: informal; chiefly historical or medical
2. a Confederate soldier during the American Civil War
Usage: historical; informal
3. any of various animals with a gray back, such as certain fish or birds
Usage: regional

Examples

• Soldiers in the trenches had to deal with graybacks during the long campaign.
• The grayback was a persistent problem in military camps before modern hygiene standards.
• Civil War historians often refer to Confederate troops as graybacks.
• The grayback fish is common in coastal waters.
• Lice infestations, particularly graybacks, were common among soldiers in earlier centuries.