The word "loonier" is an informal way to describe someone or something as crazy or insane. There are several synonyms for "loonier" that can be used to add variety and depth to your writing. Some of these synonyms include unhinged, wacko, batty, bonkers, demented, cuckoo, and nutty. Other words that can be used are eccentric, bizarre, odd, peculiar, and unconventional. It's important to choose the right synonym that matches the tone and context of your writing. Whether you're writing a story, essay, or article, using different words that have similar meanings can make your writing stand out and captivate your audience.