Body armor was a type of clothing worn to protect the wearing from dangers such as assault.
The Vulcans of Darien 224 possessed body armor which could withstand laser pistol fire, but it was less effective in resisting fire from a phaser rifle. (EV comic: "Cloak and Dagger")
The USS Enterprise NCC-1701 personnel had body armor that zipped itself up, leaving no seam. This armor was like silk, but an impact would render it rigid. (TOS novel: Planet of Judgment).