The term "vital organ" refers to the organs that are essential for the survival of an organism. These organs include the heart, lungs, brain, liver, and kidneys. Some synonyms for "vital organ" include "primary organ," "essential organ," and "critical organ." It is important to note that each vital organ carries out specific functions and any dysfunction or damage to any of these organs can severely affect the overall health of an organism. Therefore, it is crucial to take care of these vital organs through a healthy lifestyle, regular check-ups, and prompt medical attention in case of any illness or injury.