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? 
Cold = Increase in upper bass/lower mid range frequencies. Mid range and high frequencies can seem to be emphasized, seen by some as an increase in transparency/detail. 

Warm = increase in upper bass/lower mid range frequencies.  Tends to diminish mid-range  seen by some as a loss of some transparency.
You should also see the subtle color of the music. Cooler colors like chromium, silver, grey, tinges of blue through warmer colors with tinges of green, iridescent purple, yellow, gold, cabernet, tan, brown.
Subjective description of a complex audio event for the ears, which is most of the times ascribed to a cause that is the wrong culprit...Too much warm or too much cold for example are perceived and submit to an analysis of the reasons why this is so?

Genrerally people accuse one of these 2 couples....

Analog/digital recording, Tube/S.S., Turntable/dac etc

A naturalness of timbre instrument CANNOT be warm nor cold, except through a defective audio mechanical, electrical and acoustical embeddings...Timbre is neutral neither cold nor warm...Some instrument are subectively perceived colder or warmer compared to each other but their specific TIMBRE is neither cold nor warm by definition of what the timbre objectively is ( go to wikipedia)

Any one of these couples, Analog/digital,Tube/S.S. or turntable/dac, if they are rightly embedded can give a natural timbre rendition...

The only exception is a very bad design in amplifier, speakers or dac or turntable...
@newbee You replicated the initial sentences, I think you need to amend, yes? 

Post removed 
do we all assume these are terms we universally nod our heads to in agreement, whatever they are? 
Yes. That one.

Indeed, the terms don't precisely adhere to scientific criteria, but it all becomes obvious when you find your ears sweatin' or shiverin'.
Zufan, You are  right! So much for my editing skills.

The first sentence should have read "Cold = decrease.......". 

But the good part of this is I now know at least one person was reading my post. :-)
Cold- analytical, inhuman. Warm- emotional, human.

To state the extreme. Cold is a PA horn speaker and warm is all sound coming from a bass speaker. In hi-fi it's not that extreme but that is the gist of it.
Cold and warm are subjectively attributed to sound but anyway very real experience of perceived sound phenomena....

It is a characterisation of the musical timbre of a specific instrument playing in a specific room from a specific audio system, coming also from a specific recording room, which may be perceived wrongly in two different directions of the spectrum frequencies, because of bad electronical design from the recording gear or/and from the listening gear or from very bad rooms embeddings or from the 2...

But People in general prefer between 2 wrongs the least wrong one or the least agressive one, then in general the warm sound is prefered and associated with heart and body, the cold one with the brain . ... Then warm qualify something more human; cold, something more artificial...

But if the audio system is a good one, turntable or dac, S.S. or tubes; if the audio system is rightfully embedded in the house/room, the rendering of the musical specific timbre of an instrument and his perception will be very good, then relatively neutral, nor warm nor cold, because the timbre is not only, a colored-frequencies phenomenon, it is mainly a time-timing- of many sound aspects-events in a specifically acoustically designed recording and listening rooms...

A good room, a recording one or a listening one, must be the more neutral possible for frequencies perception spectrum then the complex timing of events that constitue timbre will be rightly perceived...

I look at these two terms somewhat differently, or at least use different adjectives to describe them... cold/harsh... warm/smooth, pleasing. At least to me, that is what I hear.
You are not alone, rejoice! 😊

But audio experience cannot be reduced to these qualifications....They are too gross...Audio experience is linked to the more deep question : Is the recording of this piano timbre like my audio system render it to my ears, in my room acoustic, is this piano timbre natural ? Neither cold nor warm, just right and more neutral than not ,and natural like in real life experience?

This is the question....

Happy New Year geof3....
"Warm is used by a salesman to encourage you to buy their product.

"Cold" is used to criticize a product. A salesman may use this to discourage you from this item.

Another descriptor with a positive connotation that I like is "meat on the bones".
If you're dealing with a system, or a sound, in which no agreeable balance can seemingly be struck between warm and cool, i.e. a sound that can be made to be either too cool or too warm, but offers little or no real appreciable apparent, or satisfying, 'sweet zone' in the middle, then you have a sound that is said to have little or no "inner warmth". 

A system or sound with a good deal of inner warmth will, by definition, sound neutral without also sounding threadbare. As opposed to an overtly warm sound that may be described as 'pleasing', but strictly speaking is neither accurate nor neutral.
Universally accepted as terms, but for me neither is correct when it comes to balance or neutrality.
We are all in agreement (except for Fred, he never agrees with anything) we just may not always know how to get to the good sound we're looking for.
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.... 🙃
No problem here.My favorite simile comes from an old friend who worked with me in a tiny hiend store in the 70's. We were listening to a Miracord TT (changer) with a Shure cartridge, MAC C28, MAC2105 all driving 4 ESS AMT's in a "wall" of sound configuration. After listening to most of "Dark Side of the Moon" at pretty high volume, my buddy, Gary, looked at me with a wide grimace: "Damn, that sounds like a can of nails!"Those were the days!