When you emasculate something or someone, you take away its strength. Some people believe that having a tough female boss can emasculate male employees.
The Latin emasculatus literally means "to castrate," though it is usually used figuratively, the same way emasculate is sometimes used to suggest a man isn't very manly. You may have seen bullies hassle a guy, saying he can't beat up anyone, or hit a curveball, or. . .you get the idea. Such emasculating is also insulting to women because it suggests strength and female are opposites.