Lacan uses the term "Displacement" to a great extent along the lines of Freud's formulation of the concept. According to Freud, displacement is one of the forms in which the unconscious dissociates one issue of mental content from one thought to another by way of association. According to Freud, displacement is usually manifested in dreams but also in speech.
Lacan, being engaged with language and believing the mind to be functioning as language, compared displacement with the literary function of metonymy – a contextual relation between one signifier and another in the chain of signification (or signifying chain).
see: Lacanian Terminology