Luce Irigaray introduces this term (or adopts it from Lacan's seminar Encore, where it also appears with rather less derision) to argue that, since sexuality per se is modeled on male needs and desire, it is men (in French, hommes) who relate to their one sex, even if they are in a relationship with a woman. She is thus punning on the Greek word homos ("same," as in homosexuality) and the Latin-derived French word for "man" (from the Latin homo, as in homo sapiens ). Her point is that models of sexuality, since they are designed by and for men, are in a sense always male homo-sexual models (one-sex models) that are really about how men relate sexually to one another (hommo-sexually). Irigaray's critique, which you can find in both Speculum of the Other Woman and This Sex Which Is Not One, relies on very detailed readings of Plato and Freud. Teresa de Lauretis influentially takes up Irigaray's concept, calling it "sexual indifference" and suggesting that it is central to heterosexuality.
[in De Lauretis, Teresa. The Practice of Love: Lesbian Sexuality and Perverse Desire. Bloomington: Indiana UP, 1994. ?]