Anything ineffable is unspeakably beautiful, moving, or horrible. It’s beyond expression. If something is so powerful or emotional that you can't even describe it, it’s ineffable.
Ineffable ideas and emotions are difficult to put into words. Parents might feel an ineffable sadness and pride when watching their youngest child graduate from high school. Ineffable can also be used to describe a name that is so sacred you’re not allowed to say it.This word comes from the adjective effable, which means “something that can lawfully be expressed in words,” and isn’t used much anymore.