That is a very bad sign, but before you unplug it pull the machine out from the wall and check to see if it feels hot back there as well. Then remove the lower cover and find the condersor fan motor. Its the only fan back there. I'd willing to bet that the fan is not running. The purpose of the the fan is draw air across the compressor and blow it through the condensor therefore lowering the temperature on both parts. When its not working/ running, the heat from the compressor and the condensor is pass onward to the machine and the machine then acts as a heat sink.
Also, if the machine is too close to the wall or the condensor coils are dirty you'll get the same effect, so be sure to check those things out as well
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