Federal Agency definitions applicable to Title IX …
Sexual harassment is a form of sex discrimination. Sexual harassment is unwelcome conduct of a sexual nature and can include unwelcome sexual advances, requests for sexual favors, and other verbal, nonverbal, or physical conduct of a sexual nature, such as sexual assault or acts of sexual violence.
If harassing conduct is sufficiently serious (sufficiently severe or pervasive) to deny or limit a student’s ability to participate in or benefit from the school’s program based on sex then a hostile environment based on sex may exist.
Source: Department of Justice and Department of Education’s Office for Civil Rights Joint Findings Letter to the University of Montana (May 9, 2013) http://www.justice.gov/opa/documents/um-ltr-findings.pdf