“Fifty Shades of Grey” has been rated R. That’s no surprise, but the Motion Picture Association of America’s explanation has people talking.

“The film gets the restricted rating for “strong sexual content including dialogue, some unusual behavior and graphic nudity, and for language.”

Moviegoers understand the terms “strong sexual content” and “graphic nudity,” but what’s “unusual behavior?”

Film historian Leonard Maltin interviewed by USA Today, said “that’s the first time I have heard that term” in a rating. “It’s the newest euphemism.”

Ethan Noble, chairman of MP Consulting, a company which helps studios and producers navigate the ratings process with the MPAA, told USA Today that he believes the MPAA used the term to describe the film’s sexual theme of dominance and submission, which is spelled out explicitly in the novel.

Some fans were hoping for an NC-17 rating, and that may still be a possibility should the producers decide to release a second version at a later time.