Zero cool is a slang term used to describe someone who is excessively cool or impressive beyond measure. However, antonyms for this term could be uncool, lame, or boring. Someone who is unimpressive, dull, or lacking in excitement could be considered the opposite of zero cool. Other antonyms may include clumsy, awkward or ignorant. It's important to remember that these terms are subjective and may vary from person to person. Nevertheless, by knowing the antonyms of zero cool, one can better understand its opposite meanings and use them to express themselves more accurately.