a South American tailless rodent, Hydrochaeris hydrochaeris, living along the banks of rivers and lakes, having partly webbed feet: the largest living rodent.
cap·y·ba·ra (kāp'ə-bär'ə, -bār'ə) n. A large semiaquatic rodent (Hydrochoerus hydrochaeris) of tropical South America, having short limbs and a vestigial tail and often attaining lengths of more than 1.2 meters (4 feet).