That depends where "medium" falls on the temperature scale. If we say that lukewarm is the medial point, then what you wrote makes sense. However, if we say tha

That depends where "medium" falls on the temperature scale. If we say that lukewarm is the medial point, then what you wrote makes sense. However, if we say that lukewarm is warmer than whatever the medial point is, then it makes sense to have a lukecold-like antonym. I never thought about this and this is a delightful thought exercise. Sometimes I use lukewarm to mean medium, usually when describing the weather. Kind of like where it's neither cool nor warm. However, sometimes I use it to describe something that is warmer than the ambient medium point, usually when describing bathwater and tea temperature. Re: antonyms, I see cold as an antonym of hot. Cool as an antonym of warm. Is lukewarm the midpoint between cool and warm? Sometimes, maybe, but probably it's a bit on the warmer side of neutral.