When I read any descriptions of either term, it generally explains the process of harmonizing the melody line as the highest note of a chord voicing.
I have noticed that when I see something called a chord solo, typically every melody note is harmonized into a chord in a bar. When looking at a chord melody, I'll see a chord (with melody note as the highest), followed by a single note line, then another chord, and so on.
Is that the distinction (assuming there is one)? I'd like to stop saying one thing and meaning another if these are unique terms with different meanings.