In the psychoanalytic theory of Jacques Lacan, objet petit a (object little-a) stands for the unattainable object of desire. It is sometimes called the object cause of desire. Lacan always insisted that the term should remain untranslated, "thus acquiring the status of an algebraic sign." (Écrits).
'The "a" in question stands for "autre" (other), the concept having been developed out of the Freudian "object" and Lacan's own exploitation of "otherness."