RMS Power?

kijanki,
Even though I am completely ignorant on the subject, I can fully understand why the incorrect term bugs you. I'm glad that there are people like you around to make us aware of these things.
I'm expecting Almarg to jump into this any minute...

Faulty term watts rms or rms power came most likely from around 1975 FTC standard for power rating. FTC realized, that they goofed up and 25 years later in 2000 they corrected it .

http://www.n4lcd.com/RMS.pdf

I think Roy Lewallen explained it very well:
http://eznec.com/Amateur/RMS_Power.pdf
In his summary:

The equivalent heating power of a waveform is the average power.
The RMS power is different than the average power, and therefore isn’t the equivalent heating power. In fact, the RMS value of the power doesn’t represent anything useful.
The RMS values of voltage and current are useful because they can be used to calculate the average power.

Thank you roxy54.  Almarg is much better in explaining technical merits. I'm just trying to contribute something being grateful for all things I learn here.  

imhififan, Thank you for posting.  Example of the wrong average power calculation in the second article is very interesting.  Using averaged values of voltage and current produced error of 50%.  It is very common error.  People who design test and measurement equipment (often big companies) make this mistake all the time.  For instance, when calculating mechanical power, they take average (filtered) values of speed and torque and multiply them, instead of taking instantaneous values of both, multiply and average (filter) the product - mechanical power.  For constant torque and speed it does not make a difference, but as soon as oscillatory component appears error becomes significant.  Even single percent error is very important for efficiency calculation.  Of course it has nothing to do with audio, but shows that "Power" is a muddy subject.