1.
white-fleshed fish, white meat fish
Fish with pale, white flesh, such as sea bream (tai) or flounder (hirame). A category commonly used in sushi and Japanese cuisine.
Usage
In sense 1, 白身 is often used alone to mean 白身の魚 (white-fleshed fish), especially at sushi restaurants. It contrasts with 赤身 (red-fleshed fish like tuna). In sense 2, it contrasts with 黄身 (egg yolk).
Writing
白 means "white" and 身 means "body" or "flesh." The compound refers to the white part of something.