Modesty means partially holding back. Naked parts are between the legs, buttocks, and for women breasts. To be half naked does not mean shorts and a tank top, half naked is a woman wearing shorts and no shirt. In order to be naked it has to be a certain part of the body. The opposite of being modest is flaunting. Instead of partially holding back, you partially expose. Showing cleavage is not modest, is flaunting, and it is half naked breasts. Or in men when they purposely show but crack.
But you dont have to be completely covered to be modest- because modest means moderate not complete. We know this from the Bible. How did anyone know women had long hair unless it was able to be seen? How did anyone know that Abraham's wife Sarah was like a super model if her face was covered up? They knew David was good looking, Sarah was pretty, and Christ was unbecoming- why? Because both men and women did not hide their faces, or their arms, feet, etc.
We are to blend in with the culture in which we live, but without breaking God's laws- no exposed naked parts, no tattoos, men are not to wear women's clothes, women are not to wear men's clothes, etc.
You know already, your conscience says what is to be covered and what can be exposed. No guy buys a porn magazine and says "ooh look at those shoulders and those feet." It's is sinful to look at trashy magazines, but that's my point- the areas of the body that are trashy to show in public- those are the parts to dress modestly.