From Longman Dictionary of Contemporary Englishhow so?how so?OPINIONused to ask someone to explain an opinion they have given ‘Rick’s parents are a little strange, I think.’ ‘How so?’ → how
Examples from the Corpus
how so?• "The scriptures make it perfectly clear." "Oh, how so?"• Have you noticed how so many adverts for chocolate are aimed at girls?• I do not understand how so many Black men stay sane, look after their children and strive to walk beside them.• I repeated the details of how so many of Green's family had been murdered at Auschwitz.• He does not entirely explain how so many people could lift off so quickly into the deal-making stratosphere. 