The phrase "clear as a bell" is commonly used to describe something that is very easy to understand or perceive. However, there are several antonyms that can be used to describe the opposite of something being clear as a bell. These include phrases such as "muddled as mud," "foggy as a misty morning," "ambiguous as a riddle," and "unclear as a murky pond." Each of these antonyms indicates confusion or difficulty in understanding something. Additionally, phrases like "blurred as a smudged canvas," "indistinct as a shadow," and "obscure as a dark night" can also convey a lack of clarity or sharpness.