Amy J. Devitt uses this term to describe the way genres interact with other genres.
Devitt, Amy J. "Re-fusing Form in Genre Study." Genres in the Internet: Issues in the Theory of Genre. Eds. Janet Giltrow and Deiter Stein. Philadelphia: John Benjamins Publishing Company. 2009.
"Just as all texts are intertextual, so too are all genres inter-genre-al. For the study of genre forms, that fact means that genres take up forms from the genres with which they inter-act" (Devitt 44).
Devitt's is the original use.