The term 'organ ending' is a crossword solution that can be represented by the three-letter acronym ISM. ISM stands for 'ISM, ' which is a suffix used to denote a belief, doctrine, or system of behavior. It is commonly used in the context of religious, political, and philosophical beliefs. For example, Buddhism is a religion that follows the teachings of the Buddha, and its followers are known as Buddhists. Similarly, socialism is an economic and political system based on collective ownership of the means of production, and its adherents are known as socialists.