Moral fiber is a term used to describe a person's character and integrity. It is often associated with having strong virtues and a backbone of strength. VIRTUE, which has 6 letters, is defined as moral excellence and righteousness, while SPINE, which has 5 letters, is defined as the strength and fortitude to stand up for one's beliefs. Together, these two words form the phrase 'moral fiber, ' which is used to describe a person's moral strength and courage.