What does yellow background in process table of KSysguard mean

Today I see a process's username area have a 
yellow ( different from any other process ) 
background.(as the picture shows).That process 
seems use about  100% my CPU(not showed in 
process table),and I can't kill it.When I saw The 
System Monitor Handbook I didn't find the mean 
of that.May I get the meaning of tha so I can know 
where the problem with that application.

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