A gyre is another name for a swirling vortex. Ocean gyres are large swirling bodies of water that are often on the scale of a whole ocean basin or 1000 s of kilometers across (hundreds to thousands of miles across).
Lean meats are meats with a relatively low fat content. Skinless chicken and turkey and red meat, such as pork chops, with the fat trimmed off are examples of lean meat.
Lean emphasizes absence of fat but usually suggests good health: Fattened the lean cattle for market. Skinny and scrawny imply unattractive thinness, as from undernourishment: The stray dog in the alley looked very scrawny.