What does the quote from Macbeth a deed without name mean?

"A deed without a name" (Macbeth, Act 4, Scene 1) is a phrase used by Lady Macbeth to describe the heinous and unspeakable crime that she and her husband, Macbeth, have committed in murdering King Duncan. The phrase suggests that the act is so horrible that it cannot be adequately named or described. It also conveys a sense of guilt and shame, as if the crime is so great that it cannot be acknowledged or spoken about. The phrase has come to be used more generally to describe any act that is so extreme or outrageous that it defies description or categorization.