what is "out of band termination"

Hi, there
when I see papers about distorion, I always find "out of band termination" , does anyone here give me a detailed explaination?

Thanks

Added after 3 hours 25 minutes:

any ideas?

Usually any circuit have a working bandwidth and in this bandwidth the circuit should be loaded with the optimum load
for conditional sable amplifier, if loaded with 50 ohm it should work fine without any stability problem but in case you put a filter at the output, this filter have 50 ohm in the working band but have reaction out of band which can cause the amplifier to oscillate
for unconditional stable amp no problem what evver the load is in and out of band
good luck

Usually the harmonics generated into the amplifier (that are the contributors for distortions ? IMD) it will see different impedance at the output of the amplifier, than the fundamental. These harmonics it will be reflected back to the amplifier decreasing the IMD performances.

Proper terminations at harmonic frequencies could improve dramatically the linearity performances.

http://www.maurymw.com/support/pdfs/5C-045.pdf

another form out of band termination is termination at low frequencies (modulation, "video", etc) in the bias circuitry....