In critical theory, abjection is the state of being cast off and separated from norms and rules, especially on the scale of society and morality. The term has been explored in post-structuralism as that which inherently disturbs conventional identity and cultural concepts. Julia Kristeva explored an influential and formative overview of the concept in her 1980 work Powers of Horror: An Essay on Abjection, where she describes subjective horror (abjection) as the feeling when an individual experiences or is confronted by the sheer experience of what Kristeva calls one's typically repressed "corporeal reality", or an intrusion of the Real in the Symbolic Order.

Kristeva's concept of abjection is used most commonly to analyze popular cultural narratives of horror, and discriminatory behavior manifesting in misogyny, homophobia and genocide. The concept of abjection builds on the traditional psychoanalytic theories of Sigmund Freud and Jacques Lacan, whose studies often narrowed in on the experience of the disintegration of personal distinctions, through neurosis in Freud and psychosis in Lacan.

Drawing on the French tradition of interest in the monstrous (e.g., novelist Louis-Ferdinand Céline), and of the subject as grounded in "filth" (e.g., psychoanalyst Jacques Lacan), Julia Kristeva developed the idea of the abject as that which is rejected by or disturbs social reason – the communal consensus that underpins a social order. The "abject" exists accordingly somewhere between the concept of an object and the concept of the subject, representing taboo elements of the self barely separated off in a liminal space. Kristeva claims that within the boundaries of what one defines as subject – a part of oneself – and object – something that exists independently of oneself – there reside pieces that were once categorized as a part of oneself or one's identity that has since been rejected – the abject.

However, Kristeva created a distinction in the true meaning of abjection: "It is thus not the lack of cleanliness or health that causes abjection but what disturbs identity, system, and order. What does not respect borders, positions, rules. The in-between, the ambiguous, the composite." Since the abject is situated outside the symbolic order, being forced to face it is an inherently traumatic experience, as with the repulsion presented by confrontation with filth, waste, or a corpse – an object which is violently cast out of the cultural world, having once been a subject. Thus the sense of the abject complements the existence of the superego – the representative of culture, of the symbolic order: in Kristeva's aphorism, "To each ego its object, to each superego its abject."

From Kristeva's psychoanalytic perspective, abjection is done to the part of ourselves that we exclude: the mother. We must abject the maternal, the object which has created us, in order to construct an identity. Abjection occurs on the micro level of the speaking being, through their subjective dynamics, as well as on the macro level of society, through "language as a common and universal law". We use rituals, specifically those of defilement, to attempt to maintain clear boundaries between nature and society, the semiotic and the symbolic, paradoxically both excluding and renewing contact with the abject in the ritual act.

The concept of abjection is often coupled (and sometimes confused) with the idea of the uncanny, the concept of something being "un-home-like", or foreign, yet familiar. The abject can be uncanny in the sense that we can recognize aspects in it, despite its being "foreign": a corpse, having fallen out of the symbolic order, creates abjection through its uncanniness – creates a cognitive dissonance.

"Abjection" is often used to describe the state of often-marginalized groups, such as women, unwed mothers, people of minority religious faiths, sex workers, convicts, and poor and disabled people. From a deconstruction of sexual discourses and gender history Ian McCormick has outlined the recurring links between pleasurable transgressive desire, deviant categories of behaviour and responses to body fluids in 18th and 19th-century discussions of prostitution, sodomy, and masturbation (self-pollution, impurity, uncleanness). The term space of abjection is also used, referring to a space that abjected things or beings inhabit.^{[citation needed]}

Organizational theory literature on abjection has attempted to illuminate various ways in which institutions come to silence, exclude or disavow feelings, practices, groups or discourses within the workplace. Studies have examined and demonstrated the manner in which people adopt roles, identities and discourses to avoid the consequences of social and organizational abjection. In such studies the focus is often placed upon a group of people within an organization or institution that fall outside of the norm, thus becoming what Kristeva terms "the one by whom the abject exists," or "the deject" people. Institutions and organizations typically rely on rituals and other structural practices to protect symbolic elements from the semiotic, both in a grander organizational focus that emphasizes the role of policy-making, and in a smaller interpersonal level that emphasizes social rejection. Both the organizational and interpersonal levels produce a series of exclusionary practices that create a "zone of inhabitability" for staff perceived to be in opposition to the organizational norms.