Sinewy describes something that looks or feels lean, tough, and ropy, like visible tendons and muscles under the skin. A sinewy athlete has muscles that stand out in cords and ridges rather than looking smooth or soft. Think of how a rock climber's forearms look after years of training: tight, defined, and strong, with every muscle visible.

When you see someone with a sinewy build, you're seeing strength that comes from hard use rather than bulk. A distance runner often develops a sinewy physique, different from a weightlifter's massive muscles.

Beyond bodies, sinewy can describe anything that's lean, tough, and stringy. A piece of beef might be too sinewy to chew easily. A writer's prose might be called sinewy if it's lean and powerful, with no wasted words. Even a tree branch can look sinewy when its wood twists and curves, showing the grain and texture of long, tough fibers.