The adjective stocky means wide and sturdy. The big, strong guy who works tossing heavy boxes up on a loading dock at a warehouse is stocky.
People who are stocky tend to be somewhat short and fairly heavy. Your stocky next-door neighbor is strong and solid, and his stocky bull dog is too. Interestingly, stocky meant "made of wood" back in 1400, and it was also used to distinguish "weedy" plants from more woody ones. Stocky has evolved since then to describe people with bodies "like tree trunks."