Gynecomastia is the medical term used for enlarged male breasts. The ideal male breasts are muscular and well defined, which signifies strength and masculinity. In some cases, the male breast becomes fatty and can even sag. This results in an unhealthy, out of shape, more feminine appearance. When this happens many men become quite self-conscious and may even withdraw from certain physical or social activities.
In the animated pictures of gynecomastia below, you can see how the chest of a man with gynecomastia looks in comparison to an ideal male chest.