What does fathom mean as an antoym?

As an antonym, "fathom" refers to the ability to understand or grasp something deeply, so its opposite would be a term that signifies confusion or misunderstanding. Words like "misunderstand" or "confound" capture this opposite meaning, indicating a lack of comprehension or clarity. Essentially, while "fathom" implies clarity and insight, its antonyms suggest ambiguity and obscurity.