Gender transposition is a term in linguistics to describe the substitution of a gendered personal pronoun for the other gendered form. When used to describe a woman, this would be using the pronounse his or him instead of her, and he instead of she. For men, it would be the reverse.
Often used in the argot of gay men, it can be intended either as a put-down, a self-mocking appellation, a term of endearment, or neutrally. It may be considered gay bashing or homophobic when used by heterosexual people to mock a gay person.
Use of the gender pronoun appropriate to a transgender person self-identified gender is not considered gender transposition, and does not have the same range of meaning as slang gender transposition. The pronoun corresponding to a transgendered person's gender of identification is simply considered the correct pronoun in the LGBT community and, increasingly, by mainstream society.