Tuna/ˈtuːnə/ Definition 1 of 3Pro Tip 1/3Dietary Choice ‘Tuna’ often refers to a healthy, protein-rich dietary option. She's eating more tuna to get enough protein. Pro Tip 2/3Cooking Versatility Tuna can be prepared in various ways, suggesting cuisine variety. Grilled tuna steaks are a delicious dinner option. Pro Tip 3/3Endangered Species Some tuna species are endangered, which can imply responsible consumption choices. Make sure the tuna you buy is sustainably sourced.