Yomiuri Giants
Refers specifically to the Yomiuri Giants, a professional baseball team in Japan's Central League.
巨人軍は今年も優勝を狙っている。
The Giants are aiming for the championship again this year.
巨人軍 is the full formal name of the Yomiuri Giants, while 巨人 is the everyday short form used in casual speech and headlines.
Compound of 巨人 (kyojin, 'giant') and 軍 (gun, 'army, corps'), referring to the team name.