* Not warm means something is cold.
* Knot warm is a phrase meaning something is not warm enough, or not warm at all.
While the word "knot" is often used in reference to ties, it can also be used to refer to something that is twisted or knotted. In this case, it implies that something is not smooth or flowing, which can be interpreted as not warm.
It's important to note that "knot warm" is a less common phrase than "not warm" and may not be understood by everyone.