When an amplifier is pushed to create a signal with more power than it can support, it will amplify the signal only up to its maximum capacity, at which point the signal will be amplified no further. As the signal simply "cuts" or "clips" at the maximum capacity of the amplifier, the signal is said to be "clipping." The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a distorted waveform.
Many electric guitar players will intentionally overdrive their guitar amplifiers to cause clipping in order to get a desired sound (see guitar distortion).
All amplifiers have Voltage and Current limits. Some amplifiers will use creative techniques to increase these limits or decrease them as needed. If an amplifier needs to output 20V, but is limited to +10V to -10V, then the amplifier will output +10V. It is best not to speak of a power limit outside of specific applications where the amplifier has an output impedance nearly equal to the load. For instance, a modern solid state amplifier may achieve maximum power output into a load that is ten times smaller than it can thermally handle over a long period of time.
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