大错特错

to be gravely mistaken (idiom)

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

blunder

mistake / wrong / bad / interlocking / complex / to grind / to polish / to alternate / to stagger / to miss / to let slip / to evade / to inlay with gold or silver

special / unique / distinguished / especially / unusual / very / abbr. for 特克斯[te4 ke4 si1], tex