The phrase "crazy as a loon" is often used to describe someone who is unpredictable, unstable, or insane. However, there are many antonyms that can be used to describe a person who is not "crazy as a loon". These antonyms include words such as stable, sane, rational, coherent, level-headed, and composed. A person who is described with these adjectives is typically seen as being in control of their emotions and actions, displaying sound judgment, and having a logical and steady demeanor. While "crazy as a loon" may be a colorful way to describe someone who is behaving erratically, using antonyms can help paint a more accurate and positive picture of someone's behavior.