Here's a definition:

"Under federal law and Department of Labor (DOL) policy, harassment by DOL employees of DOL employees based on race, color, religion, sex (including gender identity and pregnancy), national origin, age, disability, genetic information, sexual orientation, or parental status is prohibited. The Department of Labor does not permit harassing conduct by anyone in the workplace, including contractors.

Prohibited workplace harassment may take either of two forms. It may entail "quid pro quo" harassment, which occurs in cases in which employment decisions or treatment are based on submission to or rejection of unwelcome conduct, typically conduct of a sexual nature. Workplace harassment may also consist of offensive conduct based on one or more of the protected groups above that is so severe or pervasive that it creates a hostile or offensive work environment or when it results in an adverse employment decision (such as being fired or demoted)."

Hostile Work Environment Harassment

A hostile environment can result from the unwelcome conduct of supervisors, co-workers, customers, contractors, or anyone else with whom the victim interacts on the job, and the unwelcome conduct renders the workplace atmosphere intimidating, hostile, or offensive.

Examples of behaviors that may contribute to an unlawful hostile environment include:

discussing sexual activities;
telling off-color jokes concerning race, sex, disability, or other protected bases;
unnecessary touching;
commenting on physical attributes;
displaying sexually suggestive or racially insensitive pictures;
using demeaning or inappropriate terms or epithets;
using indecent gestures;
using crude language;
sabotaging the victim’s work;
engaging in hostile physical conduct.