Sentence:  In fact it has caused us to give <WSD>serious</WSD> thought to moving our residence south , because it is not easy for the most objective Southerner to sit calmly by when his host is telling a roomful of people that the only way to deal with Southerners who oppose integration is to send in troops and shoot the bastards down . 
Meaning of the word marked with <WSD> tags:  concerned with work or important matters rather than play or trivialities