Thermal Design Power (TDP)
The amount of heat (in watts) a processor is expected to dissipate under typical load, which the cooling system must be dimensioned for. A notoriously confusing metric: it's neither the maximum power nor an exact power consumption, and manufacturers define it differently.
Intended meaning: TDP says how much heat the cooler (fan, heatsink) must be able to lead away to keep the chip within temperature limits under a sustained load — i.e. a cooling-dimensioning figure, not an exact wattage measurement. The confusion: modern CPUs draw far MORE than their TDP in short boost periods (Intel's PL2 can be double the TDP), and how long they may do so (Tau) is governed by the motherboard → so two systems with "the same TDP CPU" can draw and perform completely differently. Moreover, Intel and AMD measure TDP differently (at base clock, at a certain temperature), so the figures aren't directly comparable. Advice: TDP is a rough indication of heat/cooling needs, not an exact consumption — look at actual power measurements (PL1/PL2, PPT) for the truth. Related to turbo boost and PL1/PL2.