But for Lacan all our discourse is in a sense a slip of the tongue:

“If this constant sliding and hiding of meaning were true of conscious life, then we would of course never be able to speak coherently at all. If the whole of language were present to me when I spoke, then I would not be able to articulate anything at all. The ego, or consciousness, can therefore only work by repressing this turbulent activity, provisionally nailing down words on to meanings. Every now and then a word from the unconscious which I do not want insinuates itself into my discourse, and this is the famous Freudian slip of the tongue or parapraxis. But for Lacan all our discourse is in a sense a slip of the tongue: if the process of language is as slippery and ambiguous as he suggests, we can never mean precisely what we say and never say precisely what we mean. Meaning is always in some sense an approximation, a near-miss, a part-failure, mixing non-sense and non-communication into sense and dialogue.”

― Terry Eagleton, Literary Theory: An Introduction