Boon companion is a phrase used to describe a close and trusted friend who brings joy and comfort to one's life. However, there are other words that share a similar meaning to boon companion. Some synonyms include confidant, comrade, ally, mate, buddy, pal, and chum. Each of these words conveys a sense of closeness and reliability, much like a boon companion. They all suggest a bond between two individuals who share a mutual trust and understanding. Whether you are describing a lifelong friend or a new acquaintance, using any of these words will communicate how much that person means to you.