Speak frankly and bluntly, be explicit, as in You can always trust Mary to call a spade a spade. This term comes from a Greek saying, call a bowl a bowl, that was mistranslated into Latin by Erasmus and came into English in the 1500s. Also see tell it like it is.

To speak directly and bluntly; to avoid euphemism: “The prosecutor said, ‘Let's call a spade a spade. You didn't borrow the money, you stole it.’”