"Mimicry" is one of two critical terms ("hybridity" is the other) in Bhabha's criticism of post-colonial literature. What Bhabha contains, in the most basic terms, is that the colonized, after a long relationship with the colonizer--a relationship that can be virtually wholly bad as in Haiti (Farming of Bones) or that can produce some benefit as in India (extensive competitive Western educational system)--has ambivalent feelings toward the colonizer: some good feelings, some desire for they have; some bad feelings, some repulsion at what they are. Bhabha contends that this ambivalence--this duality that creates a metaphorical lesion in the identity of the colonized other--is apparent in colonial and post-colonial literature and that it creates beings (who then may write literature) who are a hybrid of their own cultural identity and the colonizer's cultural identity.
As a result, mimicry occurs on various levels. At the high level, mimicry is disparaged by the culture of the colonized. At moderate levels, it goes unrealized thus unrestrained in literature. Mimicry works form the colonizer's side as well as the colonizer puts in place strategies and manipulations--like pseudo-Western governmental bodies--that mimic Western government making the subservient colonized feel independent and as authentic as the colonizer.
[Mimicry is not to be confused with the mimesis of early authors like Aristotle, Sidney and Spenser who believed that literature (especially poetry) imitated Divine truths for humans to learn and embed in their thoughts and feelings.]