No Sex Talk, Please, We're the University of Iowa:

From Iowa's sexual harassment policy, which covers student-student interactions and not just employment:

Sexual harassment occurs when somebody says or does something sexually related that you don’t want them to say or do, regardless of who it is. For example:

* Talking about their sexual experiences.
* Asking you to talk about yours.
* Telling sexual jokes, innuendoes, and stories, or comments (about your clothes or body, or someone else’s)....

Sexual Harassers

Sexual harassers can include (but aren’t limited to) professors, teaching assistants, research assistants, supervisors, co-workers, classmates, other students, acquaintances, friends, partners, dates, and strangers....

What makes someone a sexual harasser isn’t based on what they do for a living, their status as a high profile person, or where they hang out. What makes someone a sexual harasser is behavior, (including words and actions) that uses sex to be disrespectful, hurtful, embarrassing, humiliating, intimidating or frightening to you or another person....

It's not clear whether the last quoted sentence modifies the definition that I quote at the outset, but even if it does, consider how strikingly broad this rule is, both from its text and from the examples given:
Examples Red Flags / Harassing Behavior ...

* Somebody puts up sexually graphic posters, magazines, screensavers, web pages, and/or emails where you can see them....

So (as is usual) sexual harassment is not defined to include solely behavior targeted at the complainant. Nor is it limited to behavior in class or in university workplaces (where of course the professor and the supervisors may rightly constrain speech).

Rather, it deliberately covers any place and context in the university. If someone puts up a sexually themed cartoon on his dorm room door (either "sexually graphic" or presumably including "sexual joke[s]," from the first quote), that's a "red flag[] / harassing behavior." Likewise, when someone tells a sexual joke in a cafeteria to his friends at your table (even if the last sentence of the first quote is part of the definition, assume the sexual joke is disrespectful to its subject, say Britney Spears), and you hear it but you don't want to hear it, that's sexual harassment, and apparently a university disciplinary matter. Likewise if he talks about his sexual experiences in a way that's embarrassing to some other person, and you overhear (again, assume you're sitting at the table with the people he's talking to). And this at a university, where 18-to-21-year-olds live, socialize, and have sex with each other. Oy.

The Foundation for Individual Rights in Education (which passed along the pointer to the page) points out that there's also another, much narrower, definition elsewhere in Iowa's materials. But, as FIRE points out, "students at the University of Iowa are now forced to guess -- under threat of punishment -- which definition the university will choose to enforce." That's hardly proper in any circumstances, but especially when one of the definitions is so laughably broad.