What does 'cold' mean? What does 'warm' mean?


Aside from the 8 year old 'hey go open a window' replies; explain a 'cold' sounding cable? A 'warm' sounding amp?

Moreover: do we all assume these are terms we universally nod our heads to in agreement, whatever they are? 
128x128zufan
Surprised no one yet has invoked the presence of different harmonics, at different percentages in different ratios.  As @newbee says, it's at least partly a product of variations at certain points in the frequency range, but the relative presence/absence of harmonics is part of it too.
Warm: my metaphorical hand... where they may go in dream but must not go in reality for the time being.... 🙃