The term 'KNIGHT's armor' refers to the protective clothing worn by knights during medieval times. MAIL, which is a four-letter word, is one type of armor that was used. MAIL was made up of interlocking metal rings that were connected together to form a flexible and strong material. It was often worn over other pieces of armor such as plate armor or chainmail. MAIL was an effective form of protection against swords and arrows, and it was also lightweight and allowed for greater mobility.