Muscular describes someone with large, well-developed muscles that are clearly visible. A muscular athlete might have strong arms, broad shoulders, and powerful legs from years of training and exercise. You become muscular by challenging your muscles repeatedly: lifting weights, swimming, climbing, or doing push-ups makes muscle fibers grow larger and stronger over time.

The word also describes anything related to muscles themselves. A muscular injury affects muscle tissue. Muscular strength refers to how much force your muscles can produce. When doctors talk about the muscular system, they mean all the muscles in your body working together to help you move, lift, and stay balanced.

In a broader sense, muscular can describe anything that shows strength or force. A writer might have a muscular prose style, meaning their sentences feel strong and energetic rather than weak or tentative. A government might take muscular action on a problem, tackling it with force and determination instead of tiptoeing around it. This usage connects back to the physical meaning: just as muscular arms can lift heavy things, muscular ideas or actions carry real weight and power.