Power. Whenever the power of a radio transmitter, etc. is referred to it shall be expressed in one of the following forms, according to the class of emission, using the arbitrary symbols indicated:
(1) Peak envelope power (PX or pX);
(2) Mean power (PY or pY);
(3) Carrier power (PZ or pZ).
47 CFR § 2.1
Where a term or definition appears in this part of the Commission's Rules, it shall be the definitive term or definition and shall prevail throughout the Commission's Rules.