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быть круглым невеждой stresses
gen.	know as much about sth. as a pig about pineapples; not to know a B from a battledore; not to know a B from a broomstick; not to know a B from a buffalo; not to know a B from a bull's foot; not to know B from a buffalo; not to know beans; not to know chalk from cheese
idiom.	know as much about as a pig about pineapples (Yeldar Azanbayev); not to know B from a buffalo foot (сравни: не знать ни аза Bobrovska)
Makarov.	not to know B from a battledore; not to know B from a bull's foot
Makarov., amer.	not to know B from a broomstick